Why ? - Sometimes 2 chips is the right answer, and uC do follow a price.feature curve, that means extra pins often carry a lot of 'extra weight' with them.
So a 'smallest-device' + 'simplest IO expansion' (CPLD?/Logic) can be a good solution.
ct.
It might pay to verify that. The newest NXP offerings show what can be done, [LPC1340 10K/$1.49] and the peripherals can be nicer on the
32bit cores....-jg