When people discuss crypto prices, they always do so in relation to the US dollar, however this should only be correct when discussing Bitcoin - for alts the more important metric is their price in BTC.
Why? Because it indicates their performance relative to Bitcoin, so if Bitcoin rises and alts rise too, the first thing that you have to look at is their price change in BTC - when it's negative, it means that BTC outperforms them, and the opposite if it's positive.
Bitcoin is often called the king of crypto, and rightfully so - it's more stable, more safe, has higher volumes than any other coins, so when you invest in alts, you absolutely want them to outperform BTC, otherwise you are taking unjustifiable risks and get lower profits.
Indeed it is important, but most peoples in crypto sphere are often to see coin paired with usd price.
For USDT trader, im very sure most of their time are comparing bitcoin and altcoins with the USD metric.