Because of what I explained in my earlier reply.
Yes, but you added particles as an alternative to using sprites, and for those you don't use the collision overhead. Seems like you discarded that because it wasn't needed- so if a person has a case for not using collisions with sprites, then you say "well there would be no significant benefits from that method."
There are plenty of cases where a person can't use the particles because of the limited control over them, and have to resort to using sprites. It seems like the particles system is exactly something you shouldn't have created in the first place if you don't want to create multiple types of object for construct that are similar to each other.
So why not just modify the sprite object to be more customize-able and get rid of the particles? replace it with a plugin.
I know you can't do that though because you want to keep compatibility- I'm just saying..
Maybe I just don't understand this though, so if that's the case just ignore me.