It's a common tactic because it throws a wide net for everyone to find "their girl." The dev wants to give you a lot of options, so you will get invested in at least one or more of the girls and keep playing. It doesn't matter if the storylines are completed, just that you come back for the next update.
You could also look at it as a positive if the dev is receptive to feedback. I like the idea of starting the game with a lot of girls, then finding out who the players like and going from there. It's like super smash brothers. There's a character for everyone. But, again, that's assuming the dev actually cares about player feedback.
I'll say this, there are very few dev's out there who release timely updates, and most are even worse as far as quantity of content. Salty might be one of the better devs out there in this regard. That's not to say that the quality and quantity hasn't gone down like you said, but most devs have completely quit after this amount of time, or release updates extremely rarely. There was a game I saw that had its first release in over a year, and it was one scene and some bug fixes. Just the nature of this genre.
