Just go on a trip where you use your GPS a lot and take pictures with your phone and it will last half a day at best.
Modern GPS chips only need around 25mW apparently - older chips can pull 100mW though. Scanning needs a bit more power than tracking.
On phones I think the problem mainly is that the GPS needs to wake up an app that need to handle the GPS data and then do some calculations. You can easily get data ten times a second that is alot of wake up from sleep, and probably draws lots of CPU.
Basically, the phone’s battery life depends on disabling hardware components, or running them in a low power mode, as much as possible.
I think most of the drain comes from that rather than the GPS unit itself. But people might say "using my phone's GPS uses a lot of battery."