Without a shadow of doubt, the same principal applies to this forum because members here would vanish overnight if signature campaigns were ever to be banned. Almost every member here is posting because they get paid for it therefore if you take the pay away they will go elsewhere to get pay.
I suppose if theymos ever wanted to have this forum cleaned-up and have it taken back to a place where it was about newbies asking about Bitcoin on one hand and advanced members posting about core issues on the other, then he should ban signature campaigns but that decision is going to bring seismic and maybe unforeseen changes.
They knew they could get paid by posting in the other forum and knew mixers would be paying the highest rates therefore they followed where another revenue stream went. I have not read any reason from members stating they went there (or want to go there) in order to improve the other forum with their contributions.
Well, that's the sad truth. I refuse to believe someone makes an account there for other reason than money. However, I don't believe the overwhelming majority in bitcointalk would voluntarily contribute to their fellow forum users either. Perhaps occasionally, but certainly not with the same eagerness and frequency.