Re: Why ?
Well, for one thing, mobile deposits. It's nice to be able to deposit a check without physically going to the bank, and there's no way for me to do that on a PC with my bank - only the mobile app does that.
That's about all I ever do with it, but it also can show me my balance or help me find a nearby branch, etc. when I'm not home. I do all my bill paying on my (Linux) PC, but mobile is sometimes an advantage.
As for unpatched OS, whose fault is that? It's all about planned obsolescence, and most manufacturers (I'm looking at YOU, HTC) don't patch anything past 1 year. Google surprised me by supporting their hardware for a whole 2 years. Never happen, but there should be a law that they have to issue patches for everything for at least 10 years, IMHO.