It makes perfect sense to trade btc vs alts as btc is the gateway coin that you need to go through to buy most alts. If you have $100 BTC and you trade it to alts. If you make a x2 profit so you make profit of 100 $ BTC.
i think you trade to get udst profit with this way , I don't keep my trading capital in BTC, and I don't trade to earn more BTC. I trade to earn more USD.