I think it's more or less a strategic thing (like George says). If there would be a more powerful computer manufacturer then there would surely be more powerful than powersaving ARM CPUs. Or you need a chipfactory and construct your own powerful CPU (like it is done with any ARM CPU) - but then you would need a bunch of money, too. No money, no fun - sad but the truth.
I also bought a Virtual A5000 just for getting the opportunity to see RISC OS (almost) in reality. Well, a key value for keeping an alterative OS alive is to have a userbase where people buy software. So it seems pretty possible that those 3000 who have registered (I'm not registered btw) could be such a "market". Because of it's age the A5000 may not be the right choice for this (VA5000 is more nostalgia), but I think the current projects are. If an emulator helps to hold users and developers then this is also good for any other RISC OS product (as long as third party software appears/remains).
The Emulator itself is really fine - I would guess that RISC OS is one of the best (or even the best) emulated OS in our days. I was really impressed by some RISC OS features and by the consistent way of usability. I wrote a small review about VA5000 in the Techhnoids Magazine. My conclusion is that you can even be productive with this emulator and that's an important fact, too. Of course you'll always see and feel that it is not a real RISC OS Computer but VA is damn close. After all I sold the VA5000 - I now have a Mac which not runs the software. Maybe I buy a more advanced Emulator for MacOS X.