I don't think it really matters because they are people who trade against stablecoins so that any profit they have will be assured, while there are some who focus more on BTC at the same time there are others who have no preference in trading pairs. Another reason why I said it doesn't matter is that, you might come across a coin which you want to trade and find it in another trading pair which you aren't used to, does it mean you won't go ahead and trade?. Lastly, both are good trading pairs because they are unique in their own ways, thus having the right set of users or traders to keep it going.