in some cases, a woman is established in buisness or some other public situation and changing her last name would be a unacceptably hassle not just to her, but to her clients. for a real estate agent, for example, changing your name could mean losing word of mouth and starting all over.
if you are a guy, imagine what a pain in the ass it would be to change YOUR name. think of how many buisness contacts you'd have to call, web addresses/emails to change, new buiness cards to make, social security, DMV, insurance, medical records, financial things (credit cards, banks), right down to your freaking auto mechanic.
if the woman i marry wants to take my name, i will be very flattered and pleased. if she doesn't, i understand completely.