I do believe they'd disappear just because they are useless as a marketing tool.
You have a signature campaign running on your profile, right now.
At the same time you are calling them useless. The hypocrisy or at least inconsistency is entertaining.
You claim they are useless, but I bet you can name almost every company that runs a signature campaign around here (assuming you spend any significant amount of time here). They are not useless, because anybody that has the time will probably do some research on the company, organization or project to see what is up. At least this is what I do, and if it is something I believe in then I will start using, investing or playing (if it's a casino). Hard to say that they're useless, when they're doing exactly as they are intended to.
I don't understand how the fact I think signature campaigns are useless as a marketing tool and the fact I'm wearing a signature shows some kind of hypocrisy or inconsistency. I don't have to believe that signature is a good advertisement to wear it. But I have to admit that "useless" is not what I meant to say. I rather think signature campaigns aren't worth money people spend on them. Hundreds of thousands of dollars are spent to promote dozens ICOs on one particular forum (even the biggest one) - I don't think it's beneficial enough. Personally I know at least two ICOs where devs just don't want to pay for their bounty campaigns (but they probably will have to do that) just because they got almost nothing from them and have to pay a LOT of money.
Nevertheless I try to promote projects I like in the case I'm wrong about all these bounty campaigns so no hypocrisy or inconsistency at all.