I think it's a rather distasteful practice but it will always be with us. If sig campaigns are gone, buying rep will still count for something no matter what happens.
If signature campaigns gone means more than 60% traffic to this forums also will reduce. Most people are active here because of signature campaign.
Where do you get those numbers from? Signatures are fairly new and people was here before signatures, the peak of people online was in 2013 no signatures back then so deleting signatures will not affect the traffic of the forum at all, only spammers would leave, if you are here just because of signature campaigns means you are probably a spammer.