I have done research and it seems the devices supported for PSM have an always online connection(Don't know about Vita). But if they really want to get serious support to other major Android devices (The ones most people buy) then it will just be another failure, plain and simple. I am not running out to buy more expensive tablets that I have no choice but to have either a contract or some other limitation. Plus the games are over-priced.
The Vita does not have an always-online Internet connection, and does not need one to play PSM content. It only needs an Internet connection to download the content. There is no online connection requirement for playing PSM games. That has nothing to do with why PSM is not supported on other vendor's Android devices.