A sign outside a building I saw recently said, "No smoking within 20' of this door." That's a reminder that many people don't want to be near cigarette smoke.
Some estimates are that 20-25% of people in the U.S. are smokers. That means that 75-80% don't smoke, and to many of them smoking is offensive. They don't want it in or near their homes or buildings. You have a right to smoke. But if you're a smart business owner, you'll pay attention to things that offend others. If your employees are offending others, especially your clients, they need to be corrected. And stopped.
Most people try their best to avoid conflicts. They'll probably tell you not to smoke if you pull out a cigarette and start to light up, but they won't be happy that they had to say something. But they might not tell you if you stink and leave a trail of cigarette smoke in their home. They just won't invite you back. That will cost you potential referrals and sales.
It's your job, as the business owner, to make sure no one smokes and no one smells like an ashtray when you go on a job. And not smoking on a job doesn't mean that you go outside to smoke. It means you don't smoke on the job. At all.
A few years ago I hired a company to put a gate across my driveway. It took them 18 months to do a 3-week job (that's another story), but even before that I wouldn't have recommended them because their employees smoked on my property and threw their butts alongside my driveway. I'd told the owner I didn't want anyone smoking on my property. He either didn't communicate that to his employees, or his employees didn't care, because I was picking up butts after his crew left.
If you have good employees who smoke, it might be in your best interest to encourage them to quit. There are a number of programs out there that can help and you might want to pay for some or all the expense. It would be far cheaper than the leads and sales you could be missing because their cigarettes or their smell is offensive to those who don't smoke.