What is the Reason for being unable to do Cross-Platform Gifting (Gjn Client to Steam, etc.)

This seems to be just pointless and an unnecessary Complication to spending Money.*
Another Thing that’s bugging me, is that I can’t purchase (or even see for that Matter) GE Premiums on someone else’s Wishlist (at least Cross-Platform).

I’ve added the Su-22M4 WTD61 GE Premium and the Swiss F/A-18C Pack Premium to the Wishlist, and only the F/A-18C is visible. Is there any Limitation in the Code or sth. for GE Premiums to be ungiftable or visible in the First Place?

Spoiler
  • This is what I mean with that first Sentence
    grafik

None of the related Articles I could find gave a satisfying Answer to my Question.