Ya this question is very good 🙂
The more people will be Tred to this day 3 currency in the world, Because this is a one of the Best earning money for futur ,But this coin market value hinght in the crypto marketing, So more people will be trading this 3 currency iny opinion 🙂
Liquidity.
They are the most liquid cryptocurrencies and that's the reason why most of the volume is coming from those cryptocurrencies. Do you want to trade in an altcoin that doesn't really have volume or that much buyers and sellers?