I think this is a marketing strategy for them to force their users to use their exchange, This is a very bad move especially they are not that big and reputable exchange. The users will more likely avoid this exchange because of this forceful act. They are just making their users run away from them 

To think of that they aren't a big exchange, They are possibly not making such a decent amount of profit and commission from their exchange so they are forcing users to use their exchange. This is a very bad move for them.