I purchased 400$ assets last year at Unity Asset Store. Which are very useful my projects.

Projects which can only be made in unity.
And I saw very cheap DLC here too, so I bought it for my projects.

You cant have a DLC without the product on Steam, the way DLC is being update, owning GG is necessary for updates.
If I own a product, I would like to use it.
I know TGC from the Darkbasic period so I thought to buy GG and supposed that there would be all commands related to Camera, RayCasting etc will be available in GG too.
But even after email to Lee and posting on Steam forums, all I get is a reply that it will be available only when it gets on "voters list" top position. Lol. I suppose 2-3 years later.
Is exposing simple commands to LUA, so much trouble.
Its much more involving to port your Unity Projects to Steam. Whereas with GG you can easily put it on Steam. So there are some benefits with your GG projects. But I suppose you dont have enough experience about this as you dont know Unity.