On average, the weekly cost of a signature campaign is at least 1 BTC, so for a month it is about 4 BTC. Logically, why spending such a sum of money or more for something useless and has no input for your project ?. Simply, because it presents an effective method of advertising.
That is not true.There are barely any campaigns remaining which pay good amounts in Bitcoin.Right now,Chip-Mixer and Crypto-Games.net are the only campaigns which supply good quality posters along with good pay rates.Not to mention but been working with CG since 2 years now."Something useless" and "Effective method of advertising" which one is it ?They don't belong in the same sentence.
Logically no one spends huge amount of money for months if he/she doesn't gets benefit from it. Just look to primedice for example, they were first with massive sig campaign if I amn't wrong and now you see how popular they are.
They actively use other Social Media heavily for advertisement..Also the weren't the first one's to start a signature campaign..