It's not a modesty issue. It's a privacy issue. Federal employees have no need to know about travelers' surgical scars, implants, medical devices, adult diapers, etc., and privacy is a fundamental human right. Check out Bruce Schneier's writing about it.

I don't want federal agencies monitoring my e-mail either, even though some claim that monitoring private e-mails improves national security. Are you suggesting that we should just hand over our passwords at the checkpoint, too, if that's what it takes to avoid radiation and microwaves?