There's a big difference between agencies and Congressmen, especially in terms of interaction with constituents. Members of Congress are still liable to lose their seats if they don't interact with their constituents, especially the ones clamoring for legislative action. The federal agencies, on the other hand, aren't dependent on voters for keeping their jobs, and don't necessarily need to go through notice and comment procedures for all their rulemaking. These comments are going to be considered by "experts in the field," not provincial jackasses who (usually) rely on a good reputation at home to stay in DC. I really don't know how useful submitting layperson comments without credible arguments would be.