IMO, these are among the issues for the Vita's lack of success
1. Sony IPs MIA. We got Uncharted, Resistance, LBP and Killzone but Sony has so many IPs in their arsenal that have been MIA. Where was Infamous? God of War? Where are the PSP original series like Patapon and LocoRocco? The PSP became a platform where those got a new life. Syphon Filter, Ratchet, Jak, Gran Turismo, GoW, all got handheld entries which were incentive for fans of the PS1/PS2 to get them. I think a problem here has been the PS4 bc not only does Sony have their first party studios making just PS4 games, their second party ones are as well. Ready at Dawn was synonymous with PSP development, but they skipped out on the Vita to make The Order. Everyone is either making PS4 or VR titles, hence why 1st and 2nd party support has dried up with just a few releases here and there
2. Lack of 3rd party support. On a related note, 3rd parties arent really supporting it either. To go back to the PSP, 3rd parties were making original entries for their biggest IPs for the handheld. We got GTA, MGS, Final Fantasy, Kingdom Hearts. The only real push on the Vita was AC: Liberation that first year. Any 3rd party games the Vita got have mainly either been gimped multiplatform or late ports. The big publishers just havent bothered to make original games just for the system.