Since “customary” varies so widely depending on environment, I think it’s helpful when we clarify where our opinions are coming from. In my experience working in (and watching) equity productions at the SPT level, it is not customary to give a bow to the SM or crew. The curtain call is usually choreographed by the director, and we wouldn’t change that anymore than the rest of the show. That said, I have seen casts add gestures to the booth and/or backstage on the final performance of a show. When I’ve been on the receiving end of this gesture, I appreciate their thoughtfulness, but I’m not sure the audience gets that the cast is acknowledging me and the crew, and not the audience itself. I do see a difference in adding something special for the last show, and doing it every night of the run. In theaters that do a pre-show speech, I’ve heard them add a special thank you to the SM and crew on the last night, and get applause for them then, which I think is nice. As a mater of taste, I hate seeing a good show capped by a sloppy curtain call, and brining crew onto the stage, let alone the SM who one would think should be calling the show at that time, feels awkward to me, but in some situations I could see it working.