Yeah any sort of back road type thing and you'll be hosed without a spare. Plus, who wants to wait for a tow truck or some service to come help?Cost savings and the little bit of weight saved could bump up the MPG ratings a point. First thing I did with my new car is find a jack and spare for it. I spend way too much time on dirt roads with no cell service to rely on getting help with a phone call.
I've looked at some cars and there's no upfront notice that there is no spare, which could easily be forgotten about when browsing. Or some cars try to sell it as a bonus of having a can of fix-a-flat crap - yeah that'll really help when you blow a hole in the side wall.