Because of "Classicats's axiom".

If you integrate two products into one:

1.Each portion will be compromised to accommodate the other.

2.You may not get the best features that the respective individual devices get. The combo devices could be "refreshed" less often.

3. If one half breaks, you will have to do without the other while it is off getting repaired, or will break usage of the other or make it inconvenient to use.

A current new product at http://www.pcmag.com/article2/0,2704,2242734,00.asp describes an exceedingly compact laser projector that could be incorporated into a laptop that would be very useful.

Classicsat, I think you're being too critical on the combination of inventions. Think about when people first put a radio in a car. Or an air conditioner in a car. These were technically 'combined' inventions, but we would never do without them now. And my car radio isn't compromised--it has better sound than my home stereo.

When one half breaks, most people just keep using the half that's good.

Conversely, I have a component stereo system, and it seems I replace all of the components when turntables, then cassettes, next cd's go 'out of vogue.' The components aren't even broken. It would be easier for me to just get an ipod-ram stereo and throw all of that old stuff out. Ram video/movies are next.

An automobile can go both ways. If the car fails, its A/C and stereo will be useless or inconvenient (you wouldn't go out to your car to be cool or listen to the stereo, would you). Those features were added to automobiles to make motoring more enjoyable. Likewise, if either the A/C or stereo to fail, the automobile will still be operable, albeit at a less enjoyable level.

Same for an integrated projector/computer. If the computer fails, you would have to work around the computer portion (which could be easy), or have to tag along a useless projector to use a computer, in either case likely lesser featured than if they were individual units.

As for component A/V systems. That is what I have, and I have never have "had" to replace everything or numerous devices at once for the sake of one component that was added or needed replacing.

It would be less expensive to figure out why the two aren't working together in certain circumstances than to ensure that they always work together. Also, it wouldn't be more popular than the projector (which is the less useful of the two), and therefore harder to sell.