free games are only of value when they are fun to play. Current vita sales speak to that fact
There are fun and highly rated games in PS+, free or discounted.
Current Vita sales may be affected by multiple factors. Fun game alone may not work. Look at 3DS, it needed to drop price to boost its sales. It even drop the 3D display to try to get to the next level. Sony will have to find its own approach. e.g., I see people lamenting about Vita's expensive memory card.
Besides, your original point was Vita needed to be always on, which is wrong. The original Xbox One needed to be always on. Not Vita.