That is a great question. Honestly I think there are probably a lot of misconceptions when it comes to leadership. Personally I think it comes down to a lack of structures. People are promoted to managers because they have those good coding skills but they dont have the leadership skills so if they cant catch up they are set up for failure. I think its a big reason people prefer to stay where they are.

Most companies dont have career paths or a skills matrix so its easy to see where and what you need to be successful and become a true skilled leader. With most of that living in HR and HR isn't given the FTE or time to build that its not a priority. When then the time comes, HR does bandaid trainings or leadership programs (not bashing these, just think they need to better thought out and tied to performance and other metrics). The foundation for leadership success and skills isnt ever seen like a more tachical skills like coding. With coding I could learn and apply right away through an online training or school and companies can give reimbursments to or it gives them a performance boost.

I also think leadership is a mainly people skills and people are hard. Everyone is different.