Even if you're only 10% efficient, 10 hours a day is a lot, in fact especially if you're 10% efficient, you only really have 1.6 hours in your day of effectiven

Even if you're only 10% efficient, 10 hours a day is a lot, in fact especially if you're 10% efficient, you only really have 1.6 hours in your day of effectiveness, spending the majority of that daily time on a leisure activity is... costly.