If you are a market maker / arbitrageur working across multiple exchanges, US dollars can take days to settle and wire/withdrawal capacity is limited. USDT offe

If you are a market maker / arbitrageur working across multiple exchanges, US dollars can take days to settle and wire/withdrawal capacity is limited. USDT offers instant transfers, so you can rebalance across locations with ease. That's why it's being heavily used by the largest market makers in crypto.