I stayed away from this thread so far, as I thought it had strayed quite far from its original intent, and was starting to turn into another Army vs Navy thing.
As it stayed on the up-and-up, I believe a bit of historical perspective on a few points raised throughout can be of use to all.
First, it is important to remember that for the Army, the dichotomy between uniforms worn in battle (wether you call it Battledress, Combat or Cadpat) and those worn in garison (which we would call Service dress today) started in the Crimean war and was fully adopted during WWI. Before that, soldiers had only one - bright, colonial power - uniform. Trench warfare made adoption of batle dress necessary.
The navies didn't look, or need to look at a second set of "operational" clothing until the Falkland war, which is why, in most navies, they were first introduced around the late 1980's to early 1990's. Before that, sailors simply wore their sailor uniforms for everything, and since officers got white shirts, ties and jackets, that's what they wore at sea and ashore. There simply was no concept that a special "operational" uniform was required. The Falklands changed all that: the war demonstrated that the main danger to personnel was not shrapnell and concussion from HE blast anymore, but rather flash fire and hot gases from penetration by missiles still full of fuel. Protection from that was needed.
That, in itself is the reason naval personnel who served in the RCN before 1995 are seeing wearing 3's onboard as natural: it was the only uniform we had. Interestingly enough, as many here decry the dangers of wearing #3's onboard, in the pre-NCD days of the "unification" period, the officers wearing 3's were better protected than the seamen in case of fire. The green service dress (and it is still true of the current Navy DEU - save the SS shirts) was made of wool, with mostly (65%) cotton shirt, while the seamen wore the old green work dress at sea, which was all made of 100% polyester. As for shoes, in my days, we all wore the seaboots at sea, regardless of uniform, until they were unfortunately discontinued and replaced by "parade" boots. Even then, most of us, at sea, had a pair of "parade" boots that we had resoled with a proper hard rubber sole for good grip.
Even today, considering that the naval DEU is wool and cotton (save the SS shirt - but most officers I know don't use the CF issued one anyway - but buy the 100% cotton US pattern ones), working onboard wearing #3's would not be much of a danger in case of fire or other shipboard emergency.
As for the E.O's "steaming" suit - the white coveralls - there is both a practical and historical reason for those in the days of steamships: The practical one is simply that you didn't want to wear your navy wool jacket down in a room where steam engines caused both high humidity levels and heat, so something else had to be worn instead over your shirt and tie; the historical one is that on steam ships, near absolute cleanliness ("I want to be able to eat off those deck plates!") of the engine room was required to be able to immediately spot even the slightest steam leak in the process of developing - so God save the poor engine room watch who had the misfortune of being shown that the E.O. somehow got dirty on their watch (hence the white coverall).
I think someone just created a split while I was typing this, please moderators - put this post in the appropriate thread. Thanks.