Prestidigitation is all about minor effects and niceties (or not-niceties, as the case may be). Using it to clean up little messes has been a staple of the spell for as long as it has existed. While the 5e writing for it does not say you can use it to clean up mess fromthe ground, that sort of thing is what it does do, generally speaking, and is what people sue it for... so in terms of translating the spell into a video game format, it's a feature that it should get that would help make it interesting.
Yes, it's only a very small area - it's a cantrip and it's only ever going to be a small area. Out of combat, you could use it to snuff the smouldering ground between you and a treasure chest with a few repeat casts, or warm a small patch of slick ice into water so you don't fall over on the stairs (and may be with a couple more casts clean up that water, if you don't want to get your slippers wet). These are the sorts of things the spell gets used for all the time, and would translate very well into Larian's game. In combat, it wouldn't be a useful expenditure of your action unless it was a really very specifically pressing situation, and that's as it should be. It won't let you put out a raging fire, or freeze a river - it's a cantrip.
You wouldn't use Presti to clear vines - you're right that it's got no interaction there. That's why I suggested Druidcraft for that, which is, precisely, the ability to manipulate plants and vines in small ways (among its other features).
Yes. I have yet to encounter a game, where the DM would not let me use Presti to do those things. It is a staple of DnD and as a cantrip I am only limited by time to cast repeatedly (1 action is also not too long). The official wording is just restrictive to stop potential abuse.
