Re: Solderless pickups & other electronics
They'll work. I suspect that for a production guitar, it's more cost effective just to solder each end, rather than install plugs and have to deal with soldering AND crimping, etc. But yeah, if you were going to do a lot of pickup swaps, or change pots all the time, etc, it'd be very handy to have plugs. For most people though, who don't do a lot of swaps, it probably makes sense just to stick with soldering.
There's also the issue with plugs coming UNDONE sometimes. Not that solder joints can't also break, but maybe there's some concern about players who jump around or bang their guitars into stuff all the time (you know who you are!) causing the plugs to come apart. I'm sure you could get smaller locking plugs, but stuff happens.
Personally, I LIKE the idea of plugs, but I can also see why it hasn't become common.