It might not cost much for yourself, but when we're talking millions of people. Data points being recorded multiple times per day per customer, the size of that data would be huge.
The purpose is for time tracking. I am a developer but I go through periods where I work on _many_ different projects. And also I sometimes get pulled in (without warning) to support the team on client calls.
It is not uncommon for me to have 15-30 different time tracker entries for things I worked on in a single day. This is not an exaggeration. Then other days I will work on a single task for entire day.
So all of this unscheduled stuff gets lost pretty easily. Calls scheduled for an hour run only 30 minutes. Client A needed 10 minutes of support here, 20 minutes there, 5 minutes there. I want to be as fair as possible to our clients.
And related to client support, there is often the question of "who owns this bug" and who pays for the call. So I can use screenshots of the client environment to relate to the team and get more information about whether we should really be billing for the call or if that's something that needs to be improved in our software.
Also I support other developers. Skype calls with developers tend to be short. But boy can they add up. If I'm spending 3 hours a day on support overall, I really need to track that. That time needs to go into the right project at the very least.
So that's where the screenshots come in. This is not something the company asked for or have ever requested access to. They know I do this. So when I say I spent two hours supporting a client, they feel confident sending out that bill.
It actually started as one of those experiments into time lapse video. But I multitask way too much for these to be usable videos. Though I have hand picked select days and turned them into something very cool.
Quite the opposite here. I did this myself without any sort of request. This is one of the highest trust environments I have worked in. If this were forced (or expected) in any way I would be looking for a new place to be.
Meaning, the cost to record everything a person does all day, every day of the year for literally forever is not very much at all.