I disagree that it's completely useless. One should use the trading pairs with the most volume, as they present the most accurate price data (better yet a combo of high volume pairs, e.g. ETH/KRW, ETH/CNY and ETH/BTC - KRW and CNY pairs account for ≈ 60% volume, BTC accounts for only ≈ 10%)
RE: Why is always more profitable to trade alts vs BTC, not vs USD