Thether's success is based on the large number of cryto to crypto exchanges that need to go light on regulation and avoid working with banks. I don't blame them honestly, I've seen many small exchanges close down or move to other countries because their bank account was closed. Nevertheless, tether is a cancer that needs to go, even if the market would crash because of it. Unfortunately some tether clones (like TrueUSD) already appeared, so it's interesting how things will play out.