I guess, maybe, if you are very new to TF2 the crates serves a purpose, very possible opening one will net you something worth since you have no weapon but if you are willing to open your wallet, may as well buy what you want.

I could buy keys but outside the very very rare chance of an unsual hat, they hold nothing I want.

The crates pile up. I can't craft it, I can't open it so I just collect it, slowly filling my inventory of precious piles of useleness.

If it was minecraft, I'd buy a fort of it.