The 'able' part is the critical insight. Laws are too often passed that really have no ability to be enforced, but end up adding bureaucratic processes that law abiding companies have to follow. This also implies that governments need to actively clean up existing laws, which almost never happens unless there is enough support to pass a new law to actively supplant the old one.
I would argue that the reason has more to do with our utter inability to create common sense laws regarding anything "sex".
This assumes that the politician plans and has a chance to become re-elected. If this is not the case, the arguments for not advocating for such laws become much less important for the respective politician.