Why is 30 seen as such an important milestone in life to the extent that if people feel like they wasted their 20s, they pretty much feel like life is over for them?

I’ve fallen victim to this mentality myself. I turn 29 soon and my 20s have been the ideal best time of your life they are often portrayed to be. College was lonely and anxiety-inducing, I didn’t sleep around like everyone else seems to during their 20s, and I was quite isolated socially for much of the decade.

But because of the importance most people attach to turning 30, I can’t help but feel like I wasted my 20s and I’ll never get my youth back. This leads to inertia both now and when pondering the future. I feel like developing friendships and a social life at my age almost isn’t worth is because I’m so far behind. Does anyone else here dread or have previously dreaded turning 30? Why is so much significance given to it?