My GUESS is a lot of folks bought one not understanding how it might work. I know of one plugin hybrid Jeep here, I hadn't known they made one, but I see it plugged in every so often, but not routinely. The other possibility is they figured out charging is expensive from commercial outlets such as we have here. The other possibility is that folks are just lazy, they find the car runs fine without plugging it in, so they only do it on occasion, usually they feel too busy to do it.
But if you own your own home, by all means. And 110v should be adequate to charge it up overnight.