Here is the singular reason why; "Being real". Every man has his 'mumu botton'. At the same time, every man has a particular type of girl he's been envisioned to settle down with (It might not be known to him until he finds the mrs right).
If I'd wish to settle down with a Loud person for instance, and you are a loud person but pretends to be all quiet and cool, you don't expect to get a ring from me.