As Bitcoin is the highest market capitalization among all the cryptocurrencies we have right now than most of them I believe are just following Bitcoin.
So for me, especially when I am doing trading I rather trade Bitcoin than trading other altcoins especially other high market capitalization altcoins which just correlate with the price of Bitcoin most of the time, so for me, it's just the same, volume on Bitcoin is higher.
It is because bitcoin’s price influences the whole crypto market. So if ever you trade with altcoins, there are high chances that you will fail in trading as bitcoin suddenly dump its price and affects most of the altcoins. That is why most of us would want to prioritize bitcoin trading not only because of its higher volume, but the amount of returns is obviously bigger than trading with altcoins.
I think it's just wise to use btc for all activities that we do (i.e trading, investing or even when gambling) as no one can drag this coin but if you pick up other coins, there's a chance that btc can fall and it can only be dragged away, losing your gains. There's also no guarantees that when btc recovers, that alt/tok can recover because many of them are too shady.
In terms of return or profit potential, many believe that newer tokens or altcoins can supply it and not bitcoin. They think the growth rate of btc have becoming slower from time to time because its base price is already high. Well, that's up to them if they are also willing to take big risk.