I mulch small seeds especially ones that take a long time to germinate, ( Carrots, Beets, Spinach etc .. ) to maintain a moist enviroment until they break through the ground. Then I move the much away until the stem strengthens enough ( about the time they put out their first set of true leaves )

I dont usually mulch larger seeded stuff espicially beans or corn because it can tend to cause rot. The bigger seeds will absorb water and plump up so they dont need it as much.

I also use straw ( not hay )instead of grass clippings or other small /thin stuff because straw does not absorb as much moisture ( like grass clippings ) which can make the soil too wet and not allow air flow / exchange. But the Straw does prevent the soil from drying out because it catches the evaporation and also prevents the sun from hitting the bare soil.

HtH good luck