you went to the trouble of making that nice signature for the bottom of your posts. In the time it took you to make that you could have gotten a professional email address.... and no I wont send you any deals.

To answer you question it has to do with professionalism and credibility. Not bashing being honest, a gmail address makes me think you have no credibility and I promise you I am not the only one on this site who thinks that. If you want to be taken seriously then get yourself setup like a serious business.