Pics with ads?

I'm curious about this. If someone is listing an ad and has pics available, why don't they just put them in the ad instead of e-mailing them to every individual who asks for them? Also a complete description of the item, such as finish of speaker cabinets and anything else that seems significant would be helpful. It doesn't cost any extra and takes a lot less time than responding to a lot of e-mails asking these questions.
Is there a good reason for not putting this stuff in the ad that I'm not getting?