There are jobs where this isn't true!!! I want one!!! :-)
I worked for years for a company with flex time. I guess it wasn't totally flexed but it was good for me. We could officially arrive at work anytime between 6 and 8, choose lunch between 15 minutes and an hour then leave when we'd worked 8 hours. It was even more flexible for employees with more years in, I had permission to come as early as 5, and my engineer and I both liked arriving that early. There were 4 of us in the department who rode bikes and we were allowed to take lunches as long as 2 hours which we occasionally did to get out for a nice ride. Didn't do that often, but in the nice months maybe a couple of times a month.
Of course, at that job I typically worked 10 hours a day or more so it wasn't unusual for me to be the first in the drafting department to arrive and the last to leave. But, the pay was good and the flexibility was good. It also afforded me long afternoons at the lake with Myranda in the summer because I *could* come in at 5, take 15 minutes for lunch and be out of there at 1:15. With all the other hours I put in, I made it a point to do that at least once a week when she was not in school.
Sounds divine. I wish more employers would realize that giving more flexibility to workers- and treating them like adults- results in increased productivity.