JP:
Having worked in the past as a local TA, I can confirm what Marcie has told you.
Travel agents really earn their commission, and that business sector has taken some very hard economic knocks in the past 5 years. A knowlegable agent is tough to come by and trust me, they are not rolling in dough. Many do it because they love the work and their clients value their expertise.
If you don't need that kind of assistance, you'll probably want to continue to book where you can get the best price. Asking an agent to give you a kick back may make sense to you, and you may even find someone who will do it, but I think it's an unfair request to make of a professional. Remember they have bricks and morter as well as payroll and other overhead expenses. It's a slippery slope that most don't want to approach.