system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do so many loading screens go to 90% really quick, then take just as long or longer to finish the last 90%?
gpt
Here is one example:

A progress bar shows the total progress of all tasks being done. Each individual task might be different and it may not be easy to determine how long it will take (some recursive functions).

So instead of calculating the progress of each task, it will just move the progress bar forward each time one is completed. So say there are 10 tasks to do:

    Task 1 of 10 complete, move the bar to 10%.
    Task 2 of 10 complete, move the bar to 20%.
    Task 3 of 10 complete, move the bar to 30%.

And so on. Each of those tasks can take longer than the other so the progress bar can appear to jump in some places and stop in others, instead of a smooth transition from 0% to 100%.