Why are altcoin exchanged for btc and not for dollar?
having tons of altcoin is just like having bitcoin. If bitcoin grows, they grow. If bitcoin falls, they fall.
Isn't this pointless? Why not buying and selling alts for dollar?
I think it's all because Bitcoin is the currency of all cryptocurrency world and therefore all trades are on bitcoin
It's wrong. The true story is the majority of exchange sites can't provide the dollar pair because it needs more requirement on the law. Said that the majority of exchange sites which already offered fiat pair had done so many law requirements with the lawyer.
That's why a lot of exchange sites can't provide fiat pair and use bitcoin as the easiest pair.