Yes, thermobaric devices need space, like a cave, bunker, silo, WMD manufacturing plant, etc. The things that tend to be hardened against "Death From Above"™. So you research methods of penetrating the crunchy exterior to incinerate the chewy center.
Also, cooking a target with a TB bomb is much less likely to piss off the whole world than even the smallest of nuclear bombs. Nukes are like the ad hominim attack in an online debate: as soon as you use 'em, no-one will be on your side.