Alts are centralized, premined or vested the unfair way, but most importantly risky. Both coins and tokens. Nearly all crypto projects embody huge smart contract security risks which you are not aware of since you are not a smart contract auditor. Regular people get rekt. History proves 99.9% of altcoins die. Just look at a historical chart of coinmarketcap top 10. Do you remember EOS, LUNA, NEO, ... ? They once had tens of billions of dollars in them.

Pro bitcoin? If crypto market moves up, bitcoin benefits from it in any case. If bitcoin moves up, there's way smaller chance that your precious alt will follow.