they do tons of stuff at the factory that pepole like to modify... ever hear of a cold air intake? why dont they just do that at the factory....
the u-bend delete is another example. also, what about headers?? are you saying that if there was any real benefit from headers they would have just done it at the factory??
Actually, the examples you cite are flawed.
There are many performance cars that come from the factory with "headers", i.e.: tuned exhaust manifolds. Also, many cars come with a cold-air induction system. The difference is the market segment the product is aimed at.
The reason our cars didn't have these from the factory is a matter of cost, comfort, and ease of assembly and replacement. Steel headers don't last as long as cast iron, which would make the factory liable for replacement. (Many dealership-modified musclecars in the '60's and '70's came with their headers in the trunk for the owner to install to avoid warranty issues.) Our cars actually do have a "CAI", albeit a restrictive one to reduce noise. You may like the roar that a cone intake creates, but most people like a quiet induction. Both of your examples increase noise, something the engineers try to reduce on a car built for the masses. I believe the "U-bend" in the exhaust also helped speed assembly on the line.
Factory engineers are pretty smart guys, and most of them are enthusiasts. They have to design and produce a product that fits within certain parameters for a particular market segment. If they can do something better for no cost, they will generally do it. So if turning a rubber bushing 90 degrees is so great, why didn't they do it?
I believe the answer was posted above. If doing this "no-cost" modification results in less engine movement, that translates to more engine vibration being transferred to the chassis. That means less driver/passenger comfort and potentially shorter component life.
Don't get me wrong. I like to modify my cars/trucks/bikes to suit my liking and I'm willing to trade off some comfort/reliability if necessary to obtain my goals. I just want to know what, why and how the mods I'm doing are going to effect the whole package.