Kerbs
FNG
Wind Gypsy is spot on. Weight is the primary driver. But a lot of the newer stocks have higher combs and with a combination of rings that fit the scope, work without needing more riser. But there are a lot of options to adjust if needed. Some of it is preference as well.
As a generalization, adjustable combs add more weight and cost than a cheap pad or homemade riser. Some new options buck that trend with lighter weights. They do look better if that matters.