Also a lander offering unlimited oxygen and power isn't a temporary shelter. It turns it into a crutch. Why prepare for something like you have to do with almost every other mod out there when the lander will provide you with oxygen refills as needed?
If you didn't pack enough supplies for your journey, you either have to come back or in this case possibly die. Sorry. That's how games are. There's challenges you have to overcome. Turning the lander into a soda machine at a fast food restaurant (unlimited refills) takes away the challenge the mod was made to have in the first place. The rockets/lander already have cargo space for you to be able to pack extra stuff.
It was never suggested by anyone the lander should be a literally unlimited source of oxygen and power. That's something that was solely made up by you.
The idea is the lander could serve as a tool of survival. It could possibly come with an already integrated storage (rather than cluttering up the cargo space with unstackable oxygen tanks and batteries) to provide the player some support on the early part of their moon adventure. The lander GUI could in turn also provide the player with an easy-to-use interface for refilling his oxygen tanks as well as recharging any electric equipment. The lander could perhaps even possess a basic oxygen production through electrolysis, so if you can provide the lander with power and water, you can achieve an early oxygen production.