There is a tremendous amount of pressure to serve, and some families tend to treat sons that don't serve pretty harshly--i.e. cut them off financially, loss of stature in the family, etc. This behavior isn't right, but it definitely happens. A lot of guys go for no other reason than to not let their parents down, or for some promised financial reward (new BMW, college paid for, etc.) I've personally known people who have served for those very reasons.