Why ?
Would ANYONE be stupid enough to do online-banking on a portable unsecured device with an unpatched OS without a virus-scanner or firewall ?
Most people are happy to login to their banking-website from their mobile phone while using an ancient version of Android or IOS and most banks don't seem to give a f*ck !
And when people actually DO lose money the banks are more than happy to point this out so they don't have to refund the money...