Because it makes the process of selecting relationships and partners easier.

Yes, not all women enjoy casual sex or heightened sexual attention, and that's understandable and respectable.Just as not all women like increased sexual attention to them from adolescence.

But this also means that, on average, women don't need to worry about sexual selection in a partner, in the sense that, by default, a man will more often than not sexually desire a woman. Therefore, a woman can focus more on selecting a partner based on personality and compatibility, since they will already be sexually attracted to her if she likes him.

While women don't often spontaneously desire men (especially ordinary men), in this case, men will have to use their full range of partner selection. And unlike women, he will still have to worry about personality and compatibility, + he will have to pay extra attention to ensuring that she also likes him sexually him.

So, while men's increased lust may pose problems for women, it also offers an advantage that men don't.