In the first season, he really had the hots for Bon Bon. But when she returned in season three, it seemed that part of the storyline was deemphasized.

It would have ruined the show looking back on it. People can just be good friends- can't they? Plus, Michael had enough relationships while out on the road which he couldn't have done if he was in a relationship with Bonnie.

https://media.gettyimages.com/photos/season-3-pictured-david-hasselhoff-as-michael-knight-patricia-as-picture-id141270917

In a Jan 86 TV Guide interview, Patricia McPherson said that every time she suggested to Producers it was time to expand the Bon Bon character by hooking up with Michael Knight, she was shot down because it was a family show. She pointed out that explanation never made sense since Michael had a different chick almost every episode.