Here's my reasons:
1. With all the hype and hoopla devoted to it, the Segway wound up being essentially an electric scooter with a somewhat cool gyro-based stabilization mechanism. Big deal.
2. We were all under the impression that some sort of exotic new fuel supply would be powering the thing; i.e.: Stirling engine, fuel cell, hydrogen, even anti-gravity or levitation. And, it wound up being rechargeable batteries instead. Ho hum - another case of too much sizzle and not enough steak.
3. $6000 (now reduced to about $5000) is a lot to pay for what is essentially a glorified toy.
4. There's no place to sit, nor any way to carry any substantial load on it.
5. There's no way to secure it in city environments (unless you use essentially a bicycle lock and chain). And those get cut every day.
6. Its not an all-weather design. It'll work fine during the day on uncrowded paved roads and sidewalks in good weather, but that's about it. Introduce night, cold weather, rain, colichi or dirt roads, and you're SOL.
7. I couldn't use it downtown while at work because my car's not big enough to transport the thing from home. And I suspect it is heavy enough to require two people to lift it in and out of a truck.
8. And the last reason - people will look like geeks buzzing around on the thing. All they'll need to complete the effect are eyeglasses repaired with athletic tape and a pocket protector.
A couple of other FReepers about said it all in previous posts...it's been hyped-up as some revolutionary device, but doesn't serve a practical purpose for the average Joe Blow, like me.
Geting around more efficiently in warehouses, etc. would be the only practical use for the thing.
Could you imagine a city full of these things? I can, and it would be complete chaos (not to mention the personal injury lawsuits it will generate).
But, if I had a disposable income, you can bet I'd get myself one!