Here is an analogy for you.
Say you have a million dollars. You're rich, right??
Here is the catch - all million dollars is tied up in investments, realestate, etc. You have no free cash flow available for things like food gas etc.
Even though you are technically rich you are cash poor and can't take care of daily expenses.
Free cash flow = free testosterone.
Even though you have a million dollars its all in use and not available for use.
Free testosterone is needed to build muscle and other functions.