It isn't necessary. That's the point. Thinking that such a measure is necessary reveals, in my opinion, a complete loss of perspective.
If we simply allowed the police to kick down any age-groupers door and search their houses for EPO or other items, there would probably be a lot less dopers too.
A time penalty in a race does not invade my privacy. I wouldn't care if you made the penalty immediate disqualification. In fact, if that were the penalty for drafting, I would support it. Because all it would affect is standings in the race. But then, they'd have to actually enforce it.