Answer:
Looked at from a personal perspective, most people are attracted to being a manager for:-
more pay
more prestige
to exert power over others and control their actions
to get more freedom to decide what to do for themselves
to escape from being told what to do by a junior manager
to get credit for other people's ideas and hard work
Some are also motivated by
the opportunity to contribute and make a difference to a team,
trying out ideas, e.g. for business or marketing, with a much bigger budget and resources than they can get for themselves,
learning how to manage as a preliminary step to setting up their own company, all the while knowing that someone else (top management and shareholders) ulitmately pays for their learning mistakes
Downsides typically include:-
having to work longer hours, at least at first
being the first person who is blamed when things go wrong
being blamed for mistakes done by subordinates
having to deal with a constant stream of people complaining about things
A great book is written by Templar, Rules of Management. It's lighthearted and written in a funny style, but actually nails the issues very well.