Because we have Ager’s Scepter. Coldheart is called Coldheart because of the lore. It fires a physical plasma beam using a liquid fuel that serves as a coolant and is charged with arc energy.

It's not supposed to be a freeze ray , it's an Arc powered lazer with an advanced cooling system Agers Sceptre is better anyway

Coldheart is based on “Cold Fusion”. Which is a fusion reaction taking place at room temp instead of a super hot environment. Bungie’s take is that the heart/core of the weapon needs to be super cooled to produce the powerful laser. If Stasis had been around back then, maybe it would have been made that way. But with the way it is made, Arc actually makes good sense.

Ugh, not this again. It's already been explained before. It fires plasma energy (that's why it's Arc. Not to mention, you can see electricity coming from it while firing, especially with the Ornament). The name "Coldheart" refers to the cooling system/coolant that's built into it to keep the reactor from melting the gun. It's all in the lore tab on the weapon. Besides, we have Ager's Scepter for Stasis. If anything, they could improve Coldheart a bit by giving the Catalyst an additional effect where picking up Ionic Traces partially refills the magazine, and sustained damage with Coldheart while Amplified Jolts the target.

Use Ager’s Scepter