A simple test for people is to get used to working 3 hours straight without any distractions. Give it a try. You can get a whole day's work done this way.
This would be nice, if most workplaces valued efficiency. They don't, especially at the low end. Instead, they'd rather have face-time, regardless of how productive that time is. It's literally in the nature of the pay structure.
Depending on the specifics of the work, in our industry, demand for butt-in-seat time + high focus = work done + a lot of time to do your own private stuff. Devil is in the details, but this is implicitly accepted in a lot of places as long as you complete your actual work on time, because part of the reason companies want your butt in your seat for fixed amount of time per day is availability - if something suddenly happens, they want you to be there to take care of it. They do derive value from just having you in the office.
"Do your own stuff when you've finished your assigned tasks" is dicey for a couple of reasons:
1) You could be in a position where the work "never" ends. For sure, there are a reasonable number of tasks expected to be done at the end of the day, working some fraction of the day's butt-in-seat time; and when they're done, the business runs smoothly. However, recognizing this, businesses will add tasks that could be automated or designed away (e.g., answering the same inane help-desk tickets, which pile up constantly), because they "help" to secure an employee's "engagement" when they'd otherwise be free to study, optimize their performance, or simply socialize. If you're seen doing any of these, rather than the assigned tasks, you'll be docked.
2) It's difficult to bounce between tasks, including from your work-work to your personal work and back again. This is a sure-fire recipe for not being able to maintain, or even cultivate, focus. To add insult to injury, workers are often dealing with a scenario where "availability" is required of them to mask inefficiencies in the business' management or administration. This task could be done remotely, that one could be automated, a third could be grouped with a fourth if someone twisted arms to get the necessary data earlier (as has proven possible on days before a holiday). Allocating the 2 or 3 hours of the day not spent directly on work tasks would then be possible, but not when they're spread out over the course of an 8+ hour day in 10 minute chunks, or eaten up by busy work. "Hurry up and wait" is a productivity-killer.
In my experience nobody can tell what you’re doing at your desk (even if they can see the screen over your shoulder). So you can get face-time while learning for your own benefit.
