They have no obligation to support the startup beyond the initial 7% investment more so for the Series A. Companies who can't stand on their own two feet and raise money on their own simply don't deserve to survive.
I actually wish YC would take it a step further and offer an option where they don't invest any money at all. You participate in the accelerator, have access to their resources, are part of the alumni but simply don't accept the $150k and 7% equity dilution.