The first time I was ever even aware of such a thing was when I read about how Phil Spector extended the Beatle song "I Me mine" from one minute something to two minutes something by editing the second verse and chorus onto the end of the original second chorus. I would never have known had I not read it. Never thought, and still don't, that it was sterile or samey sounding.
But like many people, though I thought it made for interesting reading and was fascinating, I would never have dreamed of that kind of copy pasting.
But age has mellowed me. I still wouldn't do it !
I always just get myself or whoever is singing to sing them as they come. It's no big deal, to be honest. It's no longer for reasons of purity or authenticity or honesty or whatever. For starters, it's quicker !
However, I'm the opposite when it comes to, say, the drums. Sometimes, one chorus or verse or middle 8 or part may just contain a feel I don't like or may not be dynamic or fizzing enough or may be missing an intensity that another verse/chorus/part had. Whatever it may be, I'll take a section from somewhere else and paste it over the part I don't like and maybe "b-boof" the kick or throw in a cymbal crash just to make it different. It's easier, I suspect, with instruments and backing vocals than it may be with a lead vocal.