I understand the purpose and use of Tether, it is to allow traders to get into and out of crypto markets without cashing out directly to fiat. What doesn't make sense to me is if usdt is never been bought directly with usd then where does the usd come from to back up each usdt? and if usdt is never sold directly back to usd, why does it even matter whether Tether can cover existing usdt with usd in bank accounts? This is where my brain starts hurting because I just can't get my head wrapped around how this has worked over the last few years. It seems like it's way too easy for usdt created from nothing to have pumped the 2017 market and is keeping the markets from collapsing here in 2018. What am I missing that contradicts that this isn't what has happened?