While I'm not opposed to them as a last resort, they should hardly be your plan-a, or even your plan-b. I'm not sure you meant to imply taking them instead of anything else, but I really don't want anyone reading your message that way.
They will mobilize limited public resources that may be needed for more serious situations. Don't use them unless there is a life-threatening issue that you are indeed not prepared to deal with.
I'm trying to get better at figuring out what to carry in the van (which leaves so many more options open than a backpack), but I'd be pretty embarrassed if a break-down turned into something I needed to resort to a spot for. That said, if it did lead to a chain of events that brought on a situation that we agreed as life threatening and not something we could resolve on our own, I would swallow my pride and use one.