Ok, so this is coming from someone without too much knowledge, so I'm probably missing something basic.
On an old 10 speed bike, there are 5 sprockets on the rear hub. On a new bike, there can be 10, TWICE as many. Obviously this is because the stack of sprockets must now be thinner per sprocket. The new setup has the advantage of smaller tooth differences from lowest to highest, offering more gear choices.
My question is why don't we ever see rear wheels with 5, widely spaced sprockets of the modern, thin variety? The purpose behind this could be to use all that extra room on the rear hub to widen the space between the flanges, reduce wheel dish and have a much stronger rear wheel. Is the desire for durability over fine gear selection just too uncommon for this setup to be available? I'm especially surprised I don't see this on mountain bikes, which definitely could benefit from stronger wheels- and considering the popularity of singlespeeds, fine gear selection must not matter TOO much. Thoughts?