I changed my last name for practical reasons. First, it didn't SOUND very nice with my name, April, and second, which was even more important, was that it was a bit long. By shortening it, it became easier to use in business and social matters.
If I were to make an appointment over the phone, for example, whenever I'd give my name, everyone could spell April, but the last name sometimes needed to be spelled severall times
It was just more convenient to shorten it.