If people cant even bring themselves to muster a thank you for someone else giving up THEIR time to do something completely for free, then quite simply they aren't worth the time and effort.
Some of the work done by the artists on this threat is nothing short of stunning, you have made countless people very happy with your efforts.
Just remember, anyone requesting a sig here does so knowing that the work is being done completely free and, the least you can do is thank them for their time and efforts. Nothing is stopping you trying yourself