Because Android phones are completely secure so long as they are not rooted
The interesting question is: whom are they protecting? Me? Well, in the case of the cable company I have no doubts...
I've had no problem with any "real" banking apps yet. HBO Now failed on a rooted Nexus 4 until I used a "hide root" utility (does it mv su? I don't know), but works OK on my 1+1 running CM12.1. Good thing for them because if it didn't work I simply would have canceled the service.
When I discovered that Google Pay doesn't work on the rooted phone, then well, no Google Pay. No problem.