Why is the next new job a melee DPS?

[SecretIsland]

I watched the expansion live event yesterday to get caught up with the game. Something caught my eye, and it was that the two new jobs would be a healer and a melee DPS respectively. I found it weird because currently there are four melee DPS, and three magical and physical ranged DPS. Are melee DPS more popular in this game? It seems weird to add a fifth job to a role when two roles are currently at three.

Edit: I could not respond to everyone because of the post limit but I have upvoted your explanations! Thanks a lot for explaining.