We joked semi-seriously about combining last names. (I was a Mc, so basically turning his German last name into McGermanname lol) My husband was adopted as was my dad, so both of our last names don't really "mean" anything as far as genetics. For both of us, each last name was something we shared with our immediate family but anybody else with the last name either wasn't related or lived hundreds or thousands of miles away. There really isn't much "connection" for either of us to either last name. I'm actually more connected to my mother's maiden name (which is quickly disappearing) and my grandmother's maiden name (which will probably never disappear due to a huge, ever-producing family). It was kinda tough knowing that choosing his name would essentially end my maiden name for future generations, but in the end, it just mattered to us that we shared a name. Now that I have his name, I absolutely love that I changed it.
Also, it's been nice not having people comment about how "Irish" I must be with a Mc name. My family is actually not Irish at all, and the only reason we had a Mc name was from some drawn-out old family drama. "You must be so excited about St. Patty's Day!!!!" Nope, not Irish. "OH NO YOU MUST BE IRISH BECAUSE OF YOUR NAME!!" Nope. "NO YOU'RE WRONG! I KNOW BECAUSE I'M IRISH TOO!" Sigh, to walk away or explain the family drama that happened 50+ years ago?
In regards to choosing a completely new name, I saw it a few times in the tax prep business. Every time it came up, one or both spouses would have forgotten to change their name either at their job, on their bank account, on their Social Security card, etc. It was always a disaster for us and the clients. The first time we saw it, the people dropped off their tax docs without explaining the situation, and their folder had tax documents with 4 different last names. Our first thought was fraud lol