You could be part of a scam by not adding an email address to your QRZ bio page. Scammers will list an item and use your callsign to sell an item they do not have.
If someone goes to buy that item, they can not verify it is an actual sale and not a scam if there is not an email address on QRZ. On sites like QRZ and QTH when I am thinking about purchasing used gear, I will contact the seller directly.
I can not contact a person directly if they do not have an email address, so I skip past the item and keep looking. By having an email address as a seller you have a better chance of making a sale.
By having an email address if your not selling anything, it makes it difficult for scammers to use your callsign( your good name and reputation) during a scam. Also, someone will not get scammed in your name.