Intel makes ten to hundreds of dollars for each x86 processor they sell. They would make pennies to dollars manufacturing chips for other companies. If Intel made their own mobile chips they would have to similarly dramatically reduce their enormous margins.

In any discussion about Intel this is the point that really reigns supreme -- Intel was in the enviable state where their primary concern was always putting their own profits at risk. In the long term of course they should to move to new, growing markets (e.g. mobile), but from a closer term perspective they knew that such products, if not seriously crippled, would start chipping into their higher-end processors.

Hence why their mobile processor offerings were built on laughably dated processes, using very obsolete designs. If Intel made them better they knew that someone would figure out a way to drop 32 of them on a motherboard with a shared memory controller, etc.