Junior engineers probably aren't as appealing to FANGs. You have to train them, and teams built of senior engineers may not want to put the time into doing the training.
The main exception AFAICT is Netflix, who really prefers not to hire new grads.
If you can manage a balance of both, depending on the individuals in the team it can end up being beneficial as juniors level-up and seniors tackle the higher-level stuff.
It's a lot easier to get hired when you are given a multi-month internship to prove yourself. Instead of having to prove yourself in 5x45min interviews.
(On the other hand students don't have experience to draw on)
Junior engineers willing to burn themselves out doesn't bode well for the quality of work you're getting.