My husband and i have been married for 4 yrs now, together for 8. I need to understand why some men are not ?

I need to understand why some men are not very affectionate? He has two brothers and both seem very loving and affectionate to their wives. His mother isn't a very loving person, but his dad is. I have tried everything to have this from him. His brothers wives are bossy and not nice...at all. So why is it that a wife that isn't a good wife gets love and affection and a somewhat good wife doesn't?