Probably the bit where you need to justify your existence every morning in front of your peers and management. “I spent the day learning” doesn’t go down well, there is pressure to be seen to be busy all the time.
Programmers think Agile is for them, but it’s for the benefit of management, always was.
If you're supposed to work from 9 to 5, why would you start earlier if it doesn't benefit you to do so? If your work starts with a team meeting, why enter at 8.45? You could, but my experience is people want you to socialize then. For me (I am autistic) that's draining, not energizing. When I worked for Dutch equiv. to IRS, we had to be logged in at 9, not enter the building at 9. With Windows NT and everyone logging in at the same time this meant you had to start your computer at 8.50 or you'd be too late. I only hike quick, so I was logged in on time (even had time for a cig). Either way, they'd mainly look at the performance reports.
This goes to the GP. A government worker doesn't see any benefit. They're career is basically seniority driven if there's any advancement at all. A private sector employee would be noted for their extra effort and see a bigger bonus/be promoted.
Plenty of firms have fixed hours so you gain nothing by starting early. The office might not even be open for employees to come in early.
I've worked in various places, all private sector, and I couldn't remember ever seeing anything like this before. It finally occurred to me that perhaps they were deliberately waiting until the exact time when they were expected to be present to actually enter the building. The implication being that they'd prefer to sit in their cars rather than start their work day even a few minutes early.
Edit: Which, to be clear, is perfectly fine as far as I'm concerned--I just had never seen or done anything like that before, and I've also never worked directly for a government agency.