Because nobody has established a valid reason to bother with it.
Also, I question the assertion that it only takes a minute to fix, because I may be wrong, but my understanding is there is one Towny server parm to rule them all, one parm to bind them, and it would require tinkering with the source code to a test for whether a user is a mayor. I would rather see that effort spent on things that are actually useful.
~ @NuckleMuckle
Why this should be implemented (some not my ideas): People don't have Alts they can make co mayor to avoid the plot limit.
If you want to allow a friend to help build your town and you can't own the whole town, they suddenly can't help.
Being able to claim unlimited plots makes private towns massively easier, and you can just add your friends so they can interact with your town.
This can allow the town mayor to make more grinders and such for the town, because mayors can't place spawners on an unowned plot or a plot exclusive or below.
If this is accepted, it won't go straight to the top of the list. If all goes as it should, whatever is next in line to be implemented should be, meaning this should be close to last; so we have time to lose track of this before some one actually gets it implemented