At least in Papua New Guinea they were practical about what "publishers" could wear while engaging in field service.
In the cities, nobody wore a tie while out in FS (although we did when attending meetings).
The missionaries, pioneers and local Witnesses working in the rural areas (which is where 85% of the poulation lives) were very often having to rough it in the bush. They were allowed to dress in a very practical manner for the conditions - and usually did so.
(Imagine slogging up the muddy Kokoda Track in smooth-soled shoes , let alone a three piece suit as well!)
Bill.