At least in the consumer space (which I suspect is what you're thinking of when you say "assumes that you have an R/C transmitter in your hand"), most people over the last decade (and even now in a lot of places) are flying under some interpretation of 50+ year old model aircraft rules.

Here (.au) I'm technically not allowed to fly FPV (where I'm watching a camera view from the air thru goggles or on a screen) without having another person ready to immediately take manual control who's watching/flying "LOS" (line of sight) and complying with the regular model aircraft pilot rules.

Practically nobody actually does this, but almost everybody holds some form of manual controller and is ready to take their goggles off or look away from the screen and fly the drone manually as a regular model aircraft.

If you _want_ to "just click go on the GUI", at least some of the DJI stuff will allow you to do that. I've got a DJI Spark that I can connect/control via wifi from an iPad, and software that lets me define a mission and just click fly without needing a controller. There's still an advantage to having the controller though, it's radio as way better range than an iPad's wifi, the wifi drops out and I lose the video link (while the drone keeps flying its uploaded mission) at a hundred or so meters. If the drone and the iPad both connect instead to the DJI controller, I'll get reliable video at well over 1km. One other reason I almost always use the controller is I'm much happier launching/landing in tight locations if I fly the last few meters manually. I'll sit on the back ledge of the car boot and land 1m away from the car flying manually, but I don't trust the drone/GPS quite enough to do that, and will always find a fairly large (at least 10mx10m or so if I can) area to let it land in if it's flying totally autonomously.

To be blunt: because they're not good enough. Even ArduPilot which is probably the best mission-flying software in the open source space, or DJI who are still ahead in the commercial space, will often need manual intervention to complete a mission.

You absolutely _can_ build an ArduPilot drone that takes commands and tries to fly a mission end-to-end without intervention, but without a real-time TX link of some form, you are in hot water when it fails.

That's because Betaflight and INAV have evolved from manual/freestyle flying. ArduPilot is the more "autonomous" platform, which you can fly without a TX. You can add a USB telemetry module to your laptop and fly like that, although I've never done (and wouldn't do) that, there are many cases when you need manual control for recovery/failsafes.

I don't know where you got the idea that autonomy is why we call them drones. FPV drones are all analog and they've been around a while.

They assume you have a transmitter, because a majority of non parrot drone users are flying analog.