I have to agree with dlhuss. That wiki page is not very good.

Its not too big to use as a phone (ahem, every other smart phone).

It is expensive, but that is not a problem to most people who are looking at this type of device. Its reasonable. (Look at Archos 5 and iPod, NOT PHONES).

The other "reasons" are just stupid, so good job wiki page in killing them.

But one reason is forgotten:

(compared to everything else)

No one has one, they are niche, not much development, etc...
Yes, people will still use them, but it will be dead.