I use the same bike for the first 5 things you mentioned, and I don't need a folder or a 3-speed. It's all in your frame of mind. I just understand that I will not be able to carry as much cargo, or ride quite as fast in a group ride than if I had dedicated bikes for those purposes. But the one I have works fine, and will get me there.

I hate to admit it, but it's a misconception that you have to have the perfect bike for each and every possible function. It's nice, but definitely not required. In the name of simplicity and budget constraints, I use one bike for everything. I built the chopper in my sig as a novelty thing, but it's actually a capable bike, just doesn't have a rack or an upright riding position, so I rarely use it.