Maybe they don't, but nor do they reflect every fact. It is a game, remember, it must be playable. For the same reason that ACW infantry are not disordered by woods, so turning a whole division into skirmishers would be very...unusual, to be sure.
Rhetor, there is a PDT explanation on the old http://www.hist-sdc.com/ site for the TS games.
I once did a massive rework, doing it by 5 man incriments. The problem is that you have to completely rewrite the fire and melee tables, extend them out to 60x60, which is long and complex. It can be done, it is just complex.