Because they can't get 80fps playing World of Warcraft...
Seriously, the E71 is snappy as hell at 369MHz and I'm sure the N97 will work well. We'll find out more when the phone is released and the reviews start pouring in. That said, now that we've seen other Nokias coming out with higher speed CPU's the reign of the N97 as the flagship seems to be very short. There's no way that this phone will not be surpassed by something by the end of the year or early 2010. The N97 will still allow me to combine my N95 and my E71 and to some extent my N810. Honestly, I am very much looking forward to the next tablet since OMAP3 has been confirmed on that platform.