Performance at the cost of expansibility

Fitted a new 160GB drive the other day - after using Maxtor's MaxBlast 3 utility to add a dynamic drive overlay (as the motherboard's BIOS wouldn't recognize drives bigger than 80GB), I found out that Windows 98 (Second Edition) can't use any space above 137GB.
Got to wondering why the Windows 98 and motherboard BIOS designers decided to limit the possible size of future hard drives. In hindsight it seems obvious that drives would continue to increase in capacity, so why didn't they make the design open-ended? One answer would be built-in obsolescence, to force upgrades, but that doesn't really make sense. It seems more likely that increasing the size of recognised hard drives would've meant a drawback in performance at the level they were working with at the time. In order to force the best performance from the system then, they were obliged to limit the ability of the system to work well in the future. Do we do too much of this?