All external flash tilt, and isn't it simple and apparent to add this to the design?
I mean, take a look at this horror...
The Panasonic L1 did have such a flash, but was (I think for other reasons) largely a flop. It's hard to speculate exactly why this hasn't caught on, but I assume that it's largely because:
PS: some entry-level add-on flashes don't tilt either.
I think the market is vanishingly small for the trouble (warranties, price, etc) it would cause. You're talking about a group of people who:
Overall, its good economics for them. They're promoting their lucrative flash market and leaving the small bits to an accessory market.
No, it isn't that simple. A tiltable flash would be a lot more complex and costly, it would make the camera larger, and it would have to be much more powerful so it would drain the camera battery in no time.
It would make the camera so much more expensive that you would pay extra as much as for the external flash, but you would still not get something that is nearly as flexible and usable.
Top end SRLs doesn't even have the built in flash, because you'll want to use an external flash anyway.