Never do what your enemy wants you to do! ISIS wants US troops on the ground.
Why give them that opportunity when they can be taken out with air power? Airstrikes can effectively cripple ISIS.
Furthermore there are plenty of people in the region who have no desire to be oppressed by ISIS. Let them do the fighting for a change.
I agree the people in the region need to do more of the heavy lifting lets be honest though there is a limit to what airstrikes can do you can hurt them with airstrikes but air power alone won't defeat them, Israel has been using air power to damage and cripple Hamas for years but that has not defeated them the main reason being Hamas hides among the civilian population it's likely ISIS would use the same tactic.
That was only because Hamas had a sympathetic civilian population. Given the extremism of ISIS there aren't going to be that many places where they are going to be sheltered.
But you are correct that air power won't eliminate ISIS. That will be up to those who live in the region. If they don't have the will power then ISIS will take it over.
But there is a huge difference between being a rebel insurgency and holding and oppressing a large area. For that ISIS will need a lot more manpower. Yes, if they are successful they will have more recruits but nations like Turkey, Jordan and Saudi Arabia don't want an extremist government in the region.