Then they are just adding more money by adding more supply of the tokens.
And that's supply that they add can also help to manipulate the price of other crypto currency such as BTC and other popular crypto currency, its not a good way in my opinion It could be a bad replacement if they continue to increase supply of it especially because its not really backed by real USD. I see bad effect on it for long term if they continue doing this things.
It would be wiser to avoid Tether till they prove that they hold the fiat equivalent to their token issuance. Till than USDC and Paxos could be similar alternative as both of them are regularly verified with external auditor. In the time of rise in price many people turn into USD equivalent and it would be a disaster if USDT couldn't provide the conversion if every of them withdrew.