I'm glad someone else has noticed this. There are tons of good vids showing mock driving exams with the faults highlighted and explained which I found really useful.
It's mostly good marketing for the instructors, I think - you get to know their personality and chops before you put down the quite large amount of money required for a full suite of lessons. And it's just good PR - adding value and all that...
I know you're not telling this with bad faith, but not everything has to be done with a financial/economic objective. Some people likes to share their knowledge just for the sake of it and that's one of the things that made Internet great... Now it all has to be related with views, monetization and brand content...
It's mostly good marketing for the instructors, I think - you get to know their personality and chops before you put down the quite large amount of money required for a full suite of lessons. And it's just good PR - adding value and all that...