Being paid to take a photograph is different though. That's not speech, that's a professional service.

The two aren't mutually exclusive. I imagine you would agree that a journalist still engages in protected speech when he writes articles in exchange for compensation. Why isn't a photographer also engaging in protected speech when he takes photos in exchange for compensation?

Are you saying that an act is no longer considered speech if you're paid for it? This seems to fly in the face of innumerable legal precedents, from porn to commissioned/sponsored art works to TV shows.

As it's engaging in commerce it is subject to regulation.

There's a decent, but by no means slam dunk, case that wedding photographers engage in protected expressive conduct. The case is significantly weaker one for bakers and florists.

This is true. The case is stronger if the baker designs a custom cake or has to write a message on the cake, or if the florist designs a custom floral arrangement.