Yesterday I found that 2 of my SPRINTS spark plugs were swimming in an oil bath.

I did a lot of looking around and found that in order to cure this common problem, the club, along with a couple of the vendors, sell alloy 'O' ringed replacements.
Now, bearing in mind that I haven't taken mine out to have a look at them yet, can somebody advise me as to why the originals cant be rebuilt? I see that Rimmer's sell the 'O' rings and going down this route would be much cheaper.
So why is it that nearly everybody has swapped over to the alloy's? Can't the steel originals be overhauled satisfactorily? What am I missing?

Thanks & Cheers,
Rob