Age gaps are only a thing because men feel like they deserve a younger woman since they may have been rejected by their female peers when they were younger.
No it's because woman develop earlier and faster then men. It's because men need to be mature, lead and provide. It's takes much longer for a man to be ready to get married than a woman. The woman should ideally get married at around ~18. But at 18 most males are nowhere near ready to marry and become fathers and husbands.
So yes men do deserve a younger woman, not because they got rejected (women usually prefer older men) but because after building themselves up from nothing why would they pick a woman their age who was unwilling to support the and be around when they needed it most. Ladies you do not get to wait around at the finish line for a prince. The prince will pick a cute young virgin. Not an old lady.