Skill Gem Tags

I'm just wondering, why would a developer completely revamp the ability system and create a new one with static tag values? Why not balance your game around selectable tags, letting the player choose what kind of damage their spark ability deals?

I really liked the new skill gem system, except this damage type limitations. However, these damage type restrictions feel like an overly ambitious developer tactic from PoE1 to me. You're forcing your players to play in predetermined playstyles because that's the most logical approach with all these restrictions.