The buff from the crafting stations only works while you are inside the house/apartment/FC where the station is.
So, to make it work for GP you'd need a completely different system and I'm not sure I'd want them to put time and money into that when there are bigger issues, like the limited supply of actual houses.

The stations are also used as furniture by a lot of people so replacing them with a more generic furnishing would probably not go down well. Although if you meant keep the existing models and just make them all give a general CP buff, I'm all for it.
It's a shame people with smaller houses or apartments are penalised because they are not allowed all of them.

With Crafting as easy as it is, I don't think you need the buff for the higher levels and introducing one would probably upset people who have levelled CUL or ALC because they'd suddenly find their food/potions are redundant.