I personally hate how everyone trades in BTC pairs. I don't keep my trading capital in BTC, and I don't trade to earn more BTC. I trade to earn more USD. If a coin appreciates 50% while BTC appreciates 60%, I still made a profitable trade while missing a more profitable trade in BTC. I don't see why trading against BTC is the goal, unless you have fully removed yourself from the fiat system and pegged yourself solely to BTC. Seeing gains/losses against BTC is useless to me, the goal is more USD. If BTC tanks and you have a sell order in Satoshis on an altcoin, the order could be triggered while the USD price is break-even or even at a loss! Assessing your trades against BTC is not an accurate representation of true trading profitability.
RE: Why is always more profitable to trade alts vs BTC, not vs USD