Why do supply stations have to run out of things like grenades?

Endless grenades? Lets not go there.

True, cell refills could be a bit more frequent, but should still have a realistic limit.

You could sorta get around this, by augmenting a weapon with grenade launcher or sticky grenade launcher AND vintage heatsink. I think, haven't tried if the augments are compatible, anyone?

Or just use one of the grenade type weapons already existing (scorpion, venom or falcon atleast).