We really grew out of fire departments and are still burdened by it. (That doesn't mean all firefighters are bad medics, but EMS needs to be its own profession if we are to advance)
But in many areas it is the FDs pushing for ALS. Granted they may have their own agendas but some areas would still be all volunteer BLS ambulances if the FDs has not taken the reins. Unfortunately it would be the EMTs on the BLS squad that would be arguing their care is more than adequate and may have never pushed the issue thus giving the FD an open door.