I shoot in a studio almost exclusively. Generally it's jeans. Sometimes with a tee-shirt (a nice one), other times with a button down collar dress shirt, depending. I went to a pre- production meeting one time with ad execs, company owners, marketing people etc. and the owner of the company asked if I owned a tie. I happily answered 'no'.
I have a friend who is also a commercial photographer. He's always been a shirt and tie guy which is how I envisioned studio photographers to dress when I was considering the field in the 60's. So I guess some do, some don't again it all depends on who's coming in that day.
I work with a lot of ad agencies and design firms from all parts of the country and usually, everyone that comes into the studio is dressed much like I am, FWIW.