Much like the PSP, the Vita is the go to console for visual novels. There are loads of them cattering to different niche markets. Since those are mostly for Japanese public it gives the impression of lack of titles for the console.
That said visual novels are a bit different compared to a "regular" game and a find the Vita lacking a lot in this respect. It's a shame, the hardware is fantastic compared to the 3DS but sometimes it feels as if Sony has been gradually giving up on it. Doesn't help the fact that the 3DS is a huge success and in my eyes one of the best Nintendo systems ever despite the disappointing 3D and lack of a proper account system.
It does have its fair share of exclusives though. Too many ports though. I like ports but it needs more than that.