I think it comes down to respect for the fish.
Can you quickly land and release the fish you are seeking with a 6 wt rod?
I have seen too many steelhead caught with a noodle of a rod not up to the task and by the time the fish is landed the lactic acid build up will surely kill the fish.
Itís not about using lighter and lighter rods.
Itís about preserving our steelhead
You can definitely use a 6wt to land steelhead quickly. The one I landed took all but 4-5 minutes to land...very slow current, drag system reel and using all parts of the rod to fight/tire the fish...also using 15lbs leader helps to manage the entire set up. Now, with that said, with my 8/9wt NRX, I wouldn't have to do the ballet dance to fight the fish
...in fact, I would look like a hero standing in one place fighting the fish with one hand
With that said, would I use the same 6wt after a good rainfall and the current is stronger, no I wouldn't...that's why I have a 7wt and 8/9wt.
Back east (Ontario), I too have seen many fish floating belly up down the river as a result of guys using a 4lb leader, noodle-ish rod (centerpinning - not spey) and fighting the fish for 20 minutes. They would run up and down the river trying to fight the fish and when they finally landed it, there were hi-5's all around...after "beaching" it, covered with sand, they release the fish too quickly and the fish just goes belly up as it is exhausted.
Bringing it back to BC, on the same river last fall (Chilliwack/Vedder river), I saw a guy walk a 5-6 lbs coho down the river 40 feet yelling "Fishing ON!!!" and telling everyone to pull in their lines...by the thickness of the rod and the bend of the rod, I know he uses the same rod for Springs/Kings/Chinooks