Tempting fate here, but in over 50 years of cycling I've never had an instance where I needed help to get home. It would have to be a fairly major crash or other mechanical to stop the bike from being used, even if only in a very limited 'limp home' mode.
If you look at a modern, well maintained bike, what is there that will break to the point of stopping you riding it, albeit carefully and more slowly? I can't think of much. Yes forks / frames / bars may break (but unlikely to be sudden on a well maintained bike), same with rims, tyres, brakes, gears, chain.
If I broke a chain I'd shorten it and lose a few gears, if a tyre ruptured you can repair with a boot to get you to home / a pick up point. Not many other items left really.