It takes a while to “load up” all of those things in our minds, and it’s a bit like a balancing act, you need to keep balancing them to prevent the whole thing from crashing down
Then if you get interrupted, it is like loosing balance and things falling into a mess. Afterwards you need to sort of pick everything up again, which takes time and effort
More than a couple of those in a row are incredibly frustrating
Pg talks about this in his essay of the maker schedule vs the manager schedule: (2009) https://paulgraham.com/makersschedule.html