After a fellow forum member did a video for one of those channels you mentioned (can't remember which), a few of the "bigger power" RS6 owners like myself and a couple of others started to get forum PM's from other 'smaller' Youtubers who joined just to ask for "big" HP cars for their videos with messages such as "Hey mate your car is wicked sick bruv, mad props to you and yer crew! We wanna see on our channel to help us grow man, let me know bro!" etc and I promise I'm not exaggerating that language that much although I am having to go from memory.
I have no problem with people lending their cars top Youtubers but, for me at least, I'd prefer someone a little less "youth" and more "gentleman" like JayEmm if I was to lend my car for a YT video etc