I realize that there are terrain types; Slopes, Diers, etc. that technically would help create more realism. However, I personally stay away from them in my design (see upcoming Slaughter at Ponyri) because I don't like the attending complications. Interpreting these rules accurately, quickly, requires a lot of brain juice and time - something I'm personally not keen to do, and something I think many, perhaps most players also share. Many guys just simply don't have the time or patience for these kinds of rules, and I get that. Life and ASL is complicated enough already!
ASL has the capacity to involve, practically speaking, many kinds of additional rules that increase the realism - but at a cost. Much of the time, the cost isn't worth the benefit (also see non-terrain 'Pack Mule' or whatever, rules).
For me, I don't mind the idea of having some of these additional complicated terrain rules on hand, but also having an agreement with an opponent to ditch them at any time upon agreement. So, for instance, we can use those mapboards that have this specialized terrain but ignore some of the features (ie. Slopes), but still have a great game of it.