That's too bad. It would be nice to be able to change ownership without wiping everything out. In this case, Katt may have data and applications installed that she wants to keep on there as a secondary user, but relinquish ownership to her husband.
On the other hand, I'm not sure what affect it has being a secondary users versus the "owner" user that would matter to most people. I only have myself as a user on my machine, so have not traveled into that territory.