Obviously some alts can have significantly bigger gains than bitcoin when it comes to long term and bull runs, the last bull run from 6k to 10k for example, sure bitcoin was strong, almost a 2x but some of the top alt coins did more than a 2x even 3x. However that's only long term.
Short term I don't see any reason to trade anything other than bitcoin, especially knowing how little volume some of the other coins have, even top 10 alt coins, for example stellar only has 33m volume. So my question is, what's the point of trading stellar, for example, instead of bitcoin? You know that even if you are a whale and trade a lot, you wont be moving the market as much, if you have 1m and you trade stellar, that's already huge and we all know the 33m volume is probably not even real, a lot of it from bots trading.
It's also much easier to follow bitcoin because, well, the whole market follows bitcoin. Bitcoin dictates where the market goes.