Everything old is new again. Long, long ago, maybe in the 60's, IBM did a study on what tools to give developers to increase productivity. After a long, exhaustive study, it was found that the best things to do to increase productivity was give the programmer a door and remove the phone.
The door so the programmer could close it and there would be fewer interruptions. And get rid of the phone for the same reason.
The IBM study called the "locomotive" effect "a state of flow". And more time was wasted if they had to get into and out of that state of flow a lot.
So basically they said it didn't make any difference what tools you give people if you keep interrupting them.
That is also why, once you get started in the morning, when you look up at the clock, it is lunch time already. (if you don't get interrupted)