Just playing devils advocate (especially because this is the business I'm in), but an employees habit does sometimes affect the business. Employees who are obese, smokers, drug addicts, or subject themselves to unhealthy habits end up costing the business a ton in health insurance costs. Especially with small businesses... no word of lie I've seen 1 single employee cost a small business an extra $14,000 in health insurance premium throughout the year.
I do agree with you guys to a certain extent though... the answer isn't regulating employees outside of when they're working. But those decisions can cost their business.
I understand what you're saying from a business owner's perspective, having to provide health insurance for its employees... but you can only do so much to anticipate/avoid these costs.
You can try to weed out potentially costly employees based on health problems, drug use, obesity, etc... but what about those things that are undetectable
Why should someone not be hired because they use illegal drugs in their off time? Because you can detect it with a drug test? What about someone who chooses to drink in their off time? You aren't going to be able to figure it out with a drug test...
... and the person who uses illegal drugs could very well be the more dependable/better worker than the alcoholic.