Answering both of you at once because similar questions.
I think people like rookies because of the novelty, especially when they come in on short notice like Liam and Ollie had to. It makes for great stories : "he was called just (insert number of hours) before the race and still managed to end up P(x) ahead of (name of an established driver), unbelievable!"
The thing is, we have a 20-driver grid and there will always be someone in P20, and P19, and P18 etc. When you see the same people in these spots GP after GP and compare that to some wild card ending up in the midfield or even getting points in a one-shot race, it's easy to start thinking the drivers who are always at the back of the field are undeserving. But if you replace them with new drivers, there will still be someone in P20, and still someone in P19, and still someone in P18, etc. Let's not even get into the difference the cars they're driving make!
Novelty wears off, and then all that's left is to perform. Managing a somewhat good result (I mean even managing to just finish the race and not crashing) as a rookie in one race is genuinely impressive in its own right for specific reasons (lack of training and preparation, first time on some tracks, dealing with new settings, drivers you've never driven against, different procedures, pressure and excitement, etc.) but driving a whole year in F1 has its own challenges (adapting to tracks week after week after week, race calendar is crazy, still lack of training and preparation, delivering consistency, growing expectations, more opportunities to make mistakes, handling media duty and scrutiny, managing recovery, etc.).
The rookies are generally underprepared nowadays, the gap between F2 and F1 is gigantic and they have few opportunities to learn. So on the one hand it makes it even more impressive that Liam and Ollie performed the way they did but on the other hand it makes it more risky to hire a rookie in the cost cap era and more probable that they are not as ready as it seems to take on a full F1 season, despite their performance in a few surprise races. Simultaneously, the older drivers can't keep on going forever and someday these teams are gonna have to take the leap and hire an inexperienced driver despite the risk.
It's all a matter of subtle timing, I think. You want to make sure your rookie is as prepared as can be before you hire him so he doesn't repeatedly crashes your expensive car once he gets to drive it but you wanna make sure no one snatches this promising talent before you get a chance to sign him. At some point you find yourself on the edge of "better keep a known, proven, but aging driver" and "better put this hotheaded child who might or might not be the next big thing in my car before it's too late" territory and your choice will probably rest on your aging driver performance and consistency v. the risk of the unknown + the risk of passing up the future champion. Hiring a driver, new or not, is always a gamble.
In any case hiring or not hiring these rookies doesn't have much to do with the current RBR domination, that's more about car development. But eventually all these drivers come and all these drivers go. Generations will succeed one another, it's unavoidable. When is the question.
