I actually like achievements, but I think it would be even better if they offer little bonuses in theyr field as incentive, making them something worth to achieve ^^
It doesnt need to be big, but +1 Charm for 1st date, +Virility for first pregnant girl etc. , maybe ascending while difficulty goes up ? As most values have maximum values, raising them above those via achievements would make hunting them a good goal.
You could even lock special things to buy behind some achievements, maybe even special girls.