It had plenty of indies, mainly first and third party support.
Gravity Rush, Soul Sacrifice, Uncharted, Killzone, Tearaway, Little Big Planet and other ports didn't sell much. In fact, no vita game could sell close to 2,5mil except Minecraft, so why bother?
If you reread my post you will notice i never called them system sellers and anyway I feel a range of factors tend to push hardware sales like library- social interaction platform support etc is what pushes sales and the push rates vary.
The industry as never been homogeneous when it comes to home v portable you need to look at the patterns Even using handheld leader Nintendo and looking at their portable hardware sales aligned against home consoles with similar hardware numbers the software ratio is around 50% lower or less so we see a different buying pattern ( if you what more info about the reasons behind those figures I recommend asking Rol ) and that same pattern translates across to the Sony side with the 80 million+ PSP success can not be traced to system sellers but catering to your audience it's biggest games selling around 5- 7 million , anyway most of my reply centred on more systemic reason than lack of system sellers so I will finish by saying even Nintendo to succeed in the days of mobile needed to pivot.
Basically, Sony 1st party games alone can't do anything without the help of 3rd parties games for their platform.