Distraction during work

An article mentions about distractions and interruptions at work arising out of phone calls, visitors, etc and its impact on time to get back to work with same concentration. It says that on average, everyday a desk worker loses 2.1 hrs. Apart from colleagues in the same department, there will be visits by some unexpected visitors without notice which one has to give some time. Then there are some who keep talking on phone. You may want something, but
 they will talk about their problems without coming to the point wasting your time.
In some seminars and training programmes, there will be people who want to conduct their meetings. I do not understand, why such people attend the programmes. Instead, they can have their meetings at their office itself. The purpose of learning by attending the programmes will be lost. Some will keep talking to others or on mobile without bothering about its distraction and nuisance to others in the programme.
If this is the case with desk workers, what about those who work in the shopfloor attending machine operations, process plant operations, etc. Any distraction in the form of a visitor or phone call or thinking about personal / official jobs may lead to loss of attention / concentration and can lead to accidents. Such issues are to be monitored by shopfloor supervisors for getting the job done safely. If supervisor himself is missing in the shopfloor, then it is an invitation for accidents.