I think the only correct answer will be “there are lots of different reasons”.

My wife took my last name, even though it’s not a good one and I suggested that we pick a new one.

Here are a couple of her reasons:

1. She wanted us to have the same surname.

2. She was very close friends with my cousins growing up, so the name didn’t seem weird to her.

3. Tradition - she’d always assumed she would change her name to her husband’s name, so that seemed the most normal thing to do.