1. It creates a triangle
2. Actually gives time to develop a story between Maxie/Matt instead of just throwing them together
3. Cashing in on the popularity of Spinelli/Maxie ignoring the fact there are many of their fans that just like them as friends.
I personally wouldn't have a problem if it is a while before Matt/Maxie get together. TPTB at GH are not going to just let JC/KS sit there without at least trying to pair them together to bank on fans of Shelle. Just give it time.

Thanks to Jessica at Lookout Point for banners.