Repainting Wall

A coat of primer may seem like an unnecessary expense, but when painting interior walls, it's almost always worth it. You
should never omit primer when painting new drywall, and it's also a benefit over existing glossy or semi-gloss paints.
Primer usually isn't needed when you're painting over flat wall paint.

it has a glue-like base, drywall primer helps the paint adhere properly. If you skip priming, you risk peeling paint,
especially in humid conditions. You might blame this on the quality of paint you used, but the truth is that failure to
use primer caused the problem.