Why are the tags on the user and the tags on the ticket not distinguished?

What I mean is that the tag on the user and the tag on the ticket shouldn't be the same in the name.

This is had an effect when the agent (the agent tagged as "xxx") then agent solved the ticket, then the tag "xxx" on the ticket will be removed, and removing the field that should be mandatory then became NULL " - "

Please make ticket tags name and user field tags name must have a validation (can't be the same name)