You don't want the site to get "hacked" or something during a huge price dip
Recent evidence suggests you shouldn't trust anyone running any kind of bitcoin "storage" service, they seem to get "hacked" very easily, especially those using the ".io" domain
The .io domain is fine and in fact is preferred by many tech startups. The problem is that any business that requires trust is DOA for a big part of the community because of all those incidences.
I remember somebody posting a project a few weeks after the fortress collapsed.
Most of the advices were "Do not use the .io domain".
Certainly taints the .io "brand", in the bitcoin space at least. Personally I would have 2nd (3rd) thoughts about going near a bitcoin site now if it used .io. You never know whose Fortress it is ....