Most likely because its an MTS Trade Button, so the trade button would fit in better to take people to a market or place to buy stuff and sell stuff or perhaps, make free market the main place for your server with all npcs so users have to convinience of accessing shops, etc from anywhere using mts trade button

Correct me if im wrong but you can change the location of the free market.
Change 910000000 to the main map and 910000022 to a map inside that map like a hosue or something so users will get that same message, or u can just remove the whole
Since its OR.
Then just change
To something else

NOTE: not tested

just looking and a thought.