Because, you know.. Tether.
Seriously though, those rumors aside, Bitfinex is a pretty damn pleasant exchange to use. It's a lot more high tech than the others and it works pretty smooth.
I never keep my funds on there longer than I have to though. Don't trust my funds there with all the negativity surrounding them.
It's amazing how much people can downplay the systemic risk that Tethers pose to the ecosystem as long as price increases benefit them.