It definitely seems to be a 'generation thing'.
As Boy Entrants in the early 50's, we were not allowed any civilian clothes!
We were always in uniform unless at home on leave. To get out of camp, we had to satisfy the RAF Police on duty at the guardroom that we were appropriately dressed and still were when we arrived back.
All through my service, up to mid 60's. We wore uniform for any 'Duty Journey'. The only time I travelled out of uniform was from El Adem to Aden, staging through Khartoum. We wore KD slack's and a civvy shirt and carried Passports calling us 'Government Officials'.