You are absolutely correct.
When I'm working though its very physical. We are outside, its been 100° on average, lots of sweat, lots of water, etc. Doesn't do much for my wannabe bodybuilding goals, especially burning so many calories.
I hired a guy to help me in the office (estimating/project management etc.) So I can focus in the field when i have to.
When i don't have to be in the field (and it's when i can be in the office) is when i work out on my lunch break..
But you are correct, there's weekends.
Thanks , man.