The pitwall stand is, by any standards, an anachronism in modern F1. In the last couple of teams I have been with I have campaigned to get rid of it and save a considerable amount of freight weight, but to no avail. So why is it so important and what is going on at the pitwall while the cars are running?
Strangely, although I still regard it as an anachronism, stationing people at the pitwall has not always been the norm. Indeed, time was when there was no pitwall. It appears the trend started when it became necessary to communicate with the driver and this was, of course, long before the advent of radios in motorsport.
The pit signaller would put relevant information on a pit board to inform the driver of his position, the gaps to the cars in front and behind him, and the number of laps before his fuel stop or the end of the race.