Conversely if you have reliable payload to the lunar surface, delivering special-use lunar escape vehicles to keep on standby is a better option then having the

Conversely if you have reliable payload to the lunar surface, delivering special-use lunar escape vehicles to keep on standby is a better option then having the entire mission pay an ongoing cost for what should be an exceptional and unlikely scenario. The problem of "we need to get off the moon now" is "okay, but where are you going and what's going to be there that's more useful then where you are?" It's not unreasonable to note that a medical emergency would be much better dealt with on the moon - where you have gravity - then in orbit, where you don't. Whereas if you need to bail out and get to Earth fast (which you can't) then you'd be better off just dropping a vehicle which can do that onto the surface.