Mai's love for Qasi is great, as is her interest in Adam, but Moses presents something that is sorely needed sometimes...
Moses is Mai's stereotypical starving artist. The boy who never really left the college scene. The one whose place you're always welcome to crash at and while not glamourous, it's comfortable in its own laid back way.
Mai chose Moses for his passion for his particular art. He loves the Motown and the Jazz and he was the SINGLE person who was excited about relocating to Detroit because of the Motown scene.
He also comes in handy for the borrowing of jeans, and t shirts... and for a crash place without strings attached.