Some, like myself, find the mouse really painful to use and hate graphical interfaces when you have to randomly click to find something (while you can read a man page, grep through it and then automatize the process in custom scripts).
But it is not only about efficiency. It is about control and centralisation.
Git-send-mail works everywhere there’s an email. It allows people to use the tool they prefer. It allows them to build custom tools. It doesn’t make people dependent from a forge (you are a simple "git remote set-url" away from using a new forge).
Github forces everybody to use the same graphical interface which requires tons of JS and lot of CPU. Github forces you to accept all their changes. Github forces you to be a slave of Microsoft and contribute all your code to their IA training set. Github forces you to be notificed of stuff you don’t care.
The "Hacker culture" is first and foremost about personal freedom. And if you believe the tool are not efficient, as a true hacker, you will built others (but, spoiler, most of the time, when you become proficient enough to build you own tools, you realize how efficient the existing ones are).
Hacking is like walking. You look at walkers and you think it looks tiring to walk. So you go to the parking lot. You start your car. You go through the gate and give your driver license to the cop controlling you. You then go to the gas station. You pay with you credit card. There’s an accident in front of you, you are stuck in the traffic. You take your Google controlled GPS and ask for another itinerary. You drive. You wait at a red light, looking at your phone. A notification to pay the insurance of the car. Another one to pay for the leasing of the car itself. A light blink on the dashboard: you need to add oil and do the annual checkup of the car. You drive, you are a bit stressed and go too fast. You see a flash. Shit! Will I get a ticket? I was not that fast? You arrive at destination. There’s no room left in the parking. You start to drive around, hoping for a spot. There! You get it. It is bit small. You hope that nobody will scratch your car. For whatever reason, you learned that cars can’t be scratched so you are very careful. You get out of the car and walk a bit to the destination. Then you see them… The walkers. They went here by foot, through a path in the forest. They are smiling, even if they was some light rain.
And you ask them:
"Why don’t you guys get a car? Seriously? Walking is hard and inefficient. I can’t walk myself for than 1km before getting my legs sore."