My viewpoint is that way back when, wooden rims, especially lightweight ones, could withstand less tension than later rims. So you needed lots of spokes. The British, wisely from an engineering viewpoint, put more spokes at the rear. While wise from a duty viewpoint it is a PITA because now you needed two different rims and two different spoke lengths from the viewpoint of standardization. Also, with the American way, you could use a lighter front rim and spokes (not done much until the 70's I suppose).
Let's set aside special timetrial wheels and such.
Then someone decided (probably a marketer instead of a bean counter) that if you cut the number of spokes and added the weight to the rim, it all equaled out but was new and wonderful. So "light" rims went from 330 grams to 430 grams and you lost four spokes. Never mind that while weight equal, such a wheel has a higher polar moment of inertia.
As to placing the spokes actually saving anything, I'll defer to the world (well, western world) spoke placing champeen, Jamie Swan.
There is an engineering reason to accept the heavier rim if you want. The unexpected rim failure is buckling, which occurs in a crash. A really light rim just folds up while a relatively heavy one absorbs energy as it fails. If you have seen a crash real time on a Super Champion Medal d' Or, it is a lesson, the rim instantly buckles, snaps and pitches the rider downward at speed. There is no chance to steer out of the problem. I have seen the rim in pieces to go with the riders collar bone more than once.
Joe Bender-Zanoni Great Notch, NJ
Sheldon Brown wrote:
> Wes Oishi asked:
>
>> When did the "standard" change from 36H to 32H?
>
> Late 1980s, early 1990s
>
>> And beyond that question, why?
>
> Ah, that's the interesting one!
>
> Back in the day all bikes had 72 spokes. British bikes were 32/40,
> other countries used the less satisfactory 36/36 setup. (I've always
> maintained that if you have the same number of spokes front and rear,
> either the front wheel is heavier than it needs to be, or the rear
> wheel isn't as strong as it should be.)
>
> The exception was a few weight-weenie time trial bikes that would use
> 32 spoke wheels. 32 spoke wheels had an association with exotic, high
> end bikes as a result.
>
> Then some very clever bean counter came up with the idea of doing 32
> spoke wheels for mass produced bikes. This was a great scam, because
> the manufacturer saved a LOT of money by not having to buy and install
> those extra 8 spokes per bike. When you consider the number of bikes
> involved, it was a very substantial savings. The beauty part was that
> while they were cutting corners to save costs, they could market it as
> an _upgrade_!
>
> They made such a killing on this that we now see fewer and fewer
> spokes on newer wheels as the manufacturers pocket the savings and the
> consumer is deluded into thinking he or she is getting a better product!
>
> Sheldon "Spox" Brown
> +--------------------------------------------------+
> | Cynic: A blackguard whose faulty vision sees |
> | things as they are, not as they ought to be. |
> | --Ambrose Bierce |
> +--------------------------------------------------+