For multirotors it's just very difficult and impractical to power them with gasoline engines. If you were to build a gas powered multirotor, you'd have to have

For multirotors it's just very difficult and impractical to power them with gasoline engines. If you were to build a gas powered multirotor, you'd have to have a central engine connected to each motor by means of some complicated mechanical linkage. This would also mean you could no longer control the speeds of the motors individually, so you'd have to achieve lateral movement by pitching the propellers, like on a helicopter. All these things mean that it simply doesn't make sense to build a non-electric multirotor, it'd be massively expensive and inefficient you'd be better off going back to a helicopter. In terms of fixed wing drones, the benefit of electric over gas is mainly ease of use I believe. It's a lot simpler for someone to charge a battery and just plug it in than it is for them to fill up canisters, refuel the engine and cope with the complexities of tweaking and starting an engine. That extra effort and learning curve isn't worth it for the slightly longer slight time. For aerial mapping the go-to option is normally fixed wing drones, they can easily achieve 30-40 minutes of flight time and this is normally enough for those kind of applications.