Why Not Bomb ISIS?

Nine planes for six months; no ground fighting.  Why not?  As a matter of history, many things went wrong with the Arab Spring, but the nature of The West's commitment: providing air-support for indigenous resistance movements (I'm thinking of Libya specifically) was not one of those things. So it might work again, as in Libya.  ISIS's pattern has been to press forward until resisted, and then pull back and try elsewhere when  U.S. bombs start falling.  Like water sloshing in a bucket, back and forth between Iraq and Syria, but in smaller and smaller sloshes as their movements have been gradually constrained.  Six months from now a few of their leaders will have been killed, and their successes will have become less and less. Hopefully the movement will therefore have lost some of its savage allure, and recruiting and fund-raising abilities will be negatively effected.