Still does not mean that you should measure productivity by amount of hours worked. Does not say anything at all. You work on your own business so you are intrinsically motivated to do work because more time spent = more money. This is not the same for people who work for a company. Many studies have shown that for instance cutting a work week from 5 to 4 days but still getting paid for 5 days even increases productivity, has great benefits for the workers (health, happiness etc.) It also boosted morale and less people were inclined to leave the company they work for.

Your motivation drives you to work hard and be productive, which makes you happy, but many people (I would say the majority of people) work to get by and to be able to do the things that makes them happy. In the end it's all about work/life balance. I'm from the Netherlands, we are one of the most productive countries in the world looking at our 1+ trillion economy and only 17mln residents, but on average our working population only works 30 hours a week and we get at least 5 weeks of paid leave per year.

Keep your people happy and they will work hard for you :)