I have only used e-lock a few times. One of the first time was a month or so after I got the truck. Riding through mountains in deep snow on Christmas tree excursions.
I do not know if at that time I knew it was only effective to 20mph. I did leave it 'enabled' though. Probably helpful to get moving. I followed the tracks cut by others, but the stock F150 with highway tires (although does have M+S rating) never really skipped a beat. Took an effort to get it moving a few times though.
Since thing, probably not locked since December 2019.

The thing about a limited slip is it can cause false security. The clutches wear out. And for the person with a 15 year old truck saying "I'm glad I have limited slip" may not actually have limited slip any longer. That isn't the discussion here, but is a long term consideration.
My last vehicle was open diff and I hated it a few times because a truck with open diff is dumb. Well sort of. Most of us drive on pavement most of the time, or in loose situations that don't really require limited slip/lockers. In my previous truck, I needed to enable 4x4 to get off a soft shoulder, as simple as that is. Limited slip would just work, e-locker still requires the flip of a switch just as 4x4 would. But no need to actually use 4x4 and the e-lock is available for the one instance when needed as opposed to wearing out clutches in a limited slip every time a person makes a turn at a traffic light.
I would not buy a 2wd truck without an option to lock the rear be it e-lock, limited slip, G-80, etc. In a 4x4, I'm less concerned. So far, I've switched to 4x4 to fix problems without needing e-lock. Like turning around on a gravel road, rolling into the ditches along side of the road. Not 'into' the ditch but over the edge just enough that a 'reverse' activity will produce wheel slip with front wheels just over the edge.

For the most part -many of us have no need for limited slip or locker. It is a nice option to have when offered. If 2 identical trucks aside from locker were available, I'd buy the locker version before the open diff option without a doubt. If I am buying a 4x4 and the elocker model didn't have a feature I wanted, like 8" touch screen, I'd buy the touch screen truck before the e-locker 4x4. If 2wd drive, it would have to have a locking mechanism available.

There have been several useful instance for the elocker above that I would not consider because it's not how I utilize the vehicle....like when parking a camper on grass. Never thought about it since I'm not in that situation. For those in that situation, it sounds like the way to go! Even better is that in 4x4 in that situation, you may not be able to steer sharply and pack your rig without minor damage to the lawn if you front wheels slip.
Advantage -elocker in that situation.

 

Some F150s you can't just use the e-locker by itself. I had a 2011 FX4 and the e-locker would only engage in 4x4. Then I had a 2014 FX4 and the e-locker would engage in 4x2 and 4x4. My next 2 trucks were a 2017 and a 2020 Raptor and the e-locker will only engage in 4x4.

 

A friend had an S10 ZR2 the last year they made them, came with 31" x 10.5" BFG's and the G80 automatic locking diff. He proved that you can still do a pretty good number on the grass in 2WD with a locker and the right tires....and he proved it in MY yard. Still got my old 2WD manual trans S10 and put a Torsen from a wrecked fourth gen Camaro in it years ago, and had the Moser for my old Camaro built with a Detroit TrueTrac. Both basically do mechanically what most traction systems do electronically now. Brake based traction control plus a mechanical torque sensing diff is supposed to be pretty good.

 

My last rear 2WD vehicle was a 2002 Ford Ranger with limited slip and snow tires on the back end. I hauled some brush to the city's brush pile and it was off the gravel and onto dirt to get to the pile. Very slight downhill slope and it was greasy from rain but not soft enough to sink in to make any ruts. Drove in front first and when I went to back out back onto the gravel about 10 feet away, both rear wheels spun and would not move an inch except downwards. Did not have weight in the back as it was July. Nobody around so I started breaking up small limbs for the rear tires to grab and made a path with limbs. Never felt so helpless in a vehicle. I will not go back to a 2WD truck unless I know it will never be driven in snow or off of a hard surface.
If you are considering a 2X4 with E-Lock, please think again.

 

In that situation you probably would have driven right out if you had backed down the slope. Light truck rear end and no weight is what stopped you; weight transfer from backing in would have helped immensely. I know from experience that wet grass is very slick!

 

I was thinking this as i had a 4x2 2002 Ranger as well, though it was open diff, i would have to think about situations like this in order to get out.

 

One of the best replies here yet.

 

The G80 is terrible.

 

No E-locker on my 2016 XLT. No issues just normal driving in MN winters with 4x4 on when needed. Maybe true off-roading you'd notice. For me, it's my daily driver and it doesn't bother me not having it. Thought it would when I got it (used), but wasn't a deal breaker. The e-locker turns off above a certain speed. I have a 2015 Lariat with it and I never used it.

 

Went dove hunting earlier this year and the e-locker saved us from getting stuck in the middle on no where. We were slinging mud and the tires were caked. Put it in 4LO locked the rear diff with the e-locker and got out with minimal effort. It would have been really bad had we not had it. It's definitely nice to have have when you need it, but like some have said it's not often.