Why do people not promote Tether instead of Bitcoin?
Why should they do so, aren't they two different things, bitcoin is a decentralized digital currency that works with volatility while Tether is a stablecoin that is fix and pegged to the USD standard rate, stablecoin is not volatile like bitcoin.
Is it because there is no money to be made in Tether?
I will advise you read about stablecoin and how you can trade with it to realize profit, learning how to trade is another thing entirely you needed to add up as a skill, trading between bitcoin/stablecoin.