Many people say that cookie dough having water or milk in it makes the end result quite rock hard, and many people told me to bind the dough entirely out of fat to make it flaky. But how do the big biscuit companies make their products crispy and flaky even though their biscuits are not very greasy, and some of them have water/milk in their recipe? I have often tried to make eggless cookies with less fat in them but ended up with really hard ones. What can I do to make my cookies crisp and flaky having less butter/fat in the dough?
First, it would help to know where you are located, as "cookie" and "biscuit" are very regional terms.
Second, what commercial companies can achieve is not necessarily achievable at home. While they may use water in their products for a cheaper end product, they also have access to a lot of techniques to offset this. They may use emulsifiers or gums to make the product feel as though it has more fat in it while still using water.
Having a leaner dough though will mean a less tender end result, though it doesn't have to be hard. You could try adding a bit more leavening or baking at a lower temperature and/or for less time to keep your baked goods softer.