Not all stainless steels are the same!!

OK, whilst not wanting to get into the "my kit is made out of X, which is better than yours which is made out of Y", why is it that the manufacturers of exhausts and turbo kits seem to think that 304 stainless steel is the stuff to make stuff from? Why aren't kit's made from the superior 316L stainless? It has better anti-corrosive properties, and tests that have been conducted at my works actually give it greater yield strength than 304 (I can't remember the actual figures, but will post them in the morning). It's no more difficult to weld, and doesn't cost anymore.

Details can be found here:-

http://www.lenntech.com/Stainless-steel-316L.htm

and here:-

http://www.lenntech.com/Stainless-steel-304.htm

Even 304H would be better than 304 for a lot of the components (ie exhaust manifolds)

So basically why are all stainless steel components made out of an inferior material? After all 316L should actually reduce the likely-hood of a tubular exhaust manifold cracking. Maybe not by a lot, but it will be better.

Any thoughts?

Price? Availability?

Costs the same and is readily available. Neither of them should be an issue.

Because they want to eventually sell you another when the first one cracks after 18 months;)

304 is more easily drawn than 316 too so that could be a factor in the manufacture of piping