Oddly disappointed...

I really only have three shifts left at the restaurant where I work before I leave for my new job, so I really don't know if I should let this bother me or not. I've been there over a span of nearly ten years, and am one of only a few employees who is skilled in all of the front-of-house tasks. Yet lately, I've been getting evening shifts only, and only waiting tables instead of that and bartending as well. I have never had a problem with working where I was needed, but this evening one of my coworkers asked me to switch shifts with her tomorrow, which would allow me to bartend for the lunch shift, while she would serve for me in the evening. However, when she called to clear it with the manager, he said no. Wouldn't one think that if something were wrong with my performance, they could tell me?
Do they really mean it when they say they're sorry to see me go?
Should I even be worried?