what makes a hardware wallet better than a password secure smartphone?

[frankenmint]

I'm looking at the trezor wallets, why are they better than the Android app (with bugs ironed out) and a password secured phone?

Let's take it further and presume your browsing habits are avoided on the same cellphone.  I don't see why those aren't just a waste of money and ultimately confusing to a casual bitcoin user.

[gweedo]

It is offline and not malware can get to it.