The simple fact is that ultimately it's the seller that controls the price. One could never buy at the bid unless a seller decides to lower his asking price.
Under the theory that all buys should be at the Ask allows daytraders and people flipping the stock the ability to make money while those intending to hold for the longer term in essence give their money to those who trae the stock.
As a side note, it was stated earlier that for the market to work you always buy at the ask and sell at the bid. Every sale I have made this year on my holdings(not INIX since I haven't sold)has been at the ASK.