I think you underestimate the chore that is to invest on more than one services.
In the past, portable consoles where all about "put the thing inside and play". Playing a game was as simple as owning the console and the cartridge. In Nintendo consoles, despite them supporting digital purchases now, it's still as simple, with the game launching Icon being the first option you see shaped as a cartridge, while in Vita you have to look for the well hidden cartridge port, install it, then look for the game in this App-style menu among all the other similar looking apps, deal with all the other notifications that a 8 year old wont know what they do (wile an adult will be simply annoyed), and finally play a game that is very unlikely to be casual-friendly and good at the same time.
There is a reason Nintendo has so many hardcore fans despite having shitty hardware, and that's because both their consoles and their games are designed as Ideal starting points for new gamers!
I'm 29 years old, and If I ever have children I want them to grow up with proper games, rather those mobile junk, but as much as I like Sony, I wont be able to bring my self on getting them a Vita, as I know that they'll find it confusing and there won't be any games for them.
!