Wouldn't it be correct to say that if there exist a technology to circumvent a technological measure of access control then that measure is in fact ineffective?
The devil’s advocate argument that I can come up with for it is that it allows developers incapable of adding sufficient protection to have their work have protection of the law, rather than code.
See also: https://en.wikipedia.org/wiki/Universal_City_Studios,_Inc._v...
I don't think the linked case tried to challenge anti-circumvention provision using the reasoning I've given but it would be interesting to know if anybody else tried it :)
One particularly infuriating case involved a box that blocked the low-frequency part of a signal. That's all it took to interfere with a cable company's billing systems. Appeals court finds that was an effective measure.