Retail has shown us for a very long time that this wouldn't work, 2v2 is and always will be the most active bracket simply because it's easier to get into. They've tried fixing thing by getting rid of arena teams so people don't feel attached to whatever team they're in but in reality 2v2 will always remain the most active bracket. At least here we can give some rewards for it. Titles for 3s are different, exclusive even and have additional rewards that can't be obtained otherwise.
In the past we even gave out money, coins and a variety of rewards, requests, special titles. Not much has changed, incentive is not the issue, rather the desire of players. Hopefully, the next arena season with the requirements and rewards in mind should be more active and more entertaining, with the idea of a possible WIT Series 2 coming up.