In pretty much every profession the younger, up and coming, guys (managers, coaches, etc.) all want to be "the guy". The President, CEO, Head Coach.
When they get there, if they moved up too quickly they often find it wasn't what they believed it would be or are not ready for all the challenges.
They'll still be coaching, but at the top there's much more to the job. There's politics and schmoozing you're not involved with as an assistant, along with other requirements to successfully run a "program". The "program" you build makes you or breaks you and while a few can rush it and succeed there are many who jump too soon and aren't ready for all the challenges or take a job at which even JC couldn't be successful.
So, if they love working with and developing kids and don't enjoy the other aspects of the job it won't be the dream situation they envisioned. Or, if they jump too high too soon they may not be ready to overcome all the challenges.
Look at Dan Hurley's career path. He built his resume' with over a decade at a prominent high school followed by great success at a low major, then similar success at a mid major before coming to UConn. He was ready for the challenge in every way.
Dan Hurley can give his assistants great advice, similar to the advice he probably received from his Dad, George Blaney and others, and help them make the best decision as to what's right for them and what job has real promise for a great future.