As Phillip mentioned, I think you need to analyze what you will be using the part for. If you need an 8052 to go that fast you probably ought to evaluate whether you should be using some other processor.

That said, I think the main reasons are:

1. Desire to keep price in-line with what 8052's are used for.
2. Desire to minimize power consuption.
3. Desire to reduce EMI.
4. Desire to avoid needing an air conditioner piggy-backed to the 8052 for CPU cooling.

Craig Steiner