When it comes to maintaining your job, you need to make sure that you are always on top of your game. Being on top of you game means that you will be on things before anyone else. That is the best thing to do if you wanna be promoted or given a raise often.
However, in the office, if you lead a team, you will now be the one responsible of their skill upgrades. Of course they can work on their own skills on their own time. But on the other hand, as a team leader, if you want your team to prosper, you will need to ensure that you are doing your part in leveling your team up.