Two 16-bit numbers could be combined to form a 32-bit pointer. Used as segment<<4+offset they just form a 20-bit pointer. Feels like wasting 12 bits to me.
You can also look at 8086 segment/offset addressing as an attempt to avoid wasting 12 bits when using pairs of 16 bit registers to represent a 20 bit address, by allowing implicitly-sized <=64k byte segments to align on arbitrary 16 byte boundaries vs. the 64k byte alignment implied by segment<<16 + offset.
