Why is NONE of the keyboard / organ brands capable to produce tonewheel-sound like Hammond and NI B4 both do ?
--------------------------------------------

Because the B4 is a computer program running all the time using A LOT of CPU power. The computing power of an arranger is not at par with that of a current windows or mac machine by no means.

Also because only Native Instruments has developed such a software. But it is interesting that about 1 year ago, Native Instrument's developement premises were broken-in and some work stolen.

However, there is definetely a lot of potential in this type of approach to musical instruments. It beats sampling, specially in the dynamics aspect of an instrument. With the B4 simulator one gets GOOD performance even at the highets keys. Why? Because there is a virtual wheel turning and producing sine-wave sounds as in the real instrument. There is no interpolation as in sampled instruments. Because of the high resource demand, latency was a problem, but not any more with the new PC-cpu's and advances. Those guys at Native Instruments are geniuses.