About 5 years ago I lost the best engineer on my team, and he told me why on the phone after he had already submitted his resignation to HR.
He was the person I went to with every hard problem. Once I asked him to fly to California on less than 24 hours notice to lead the final install on a project and then commission it, with the two overlapping for most of the trip. He went, and he was excellent at both, which is a rare combination in one person. He worked with a calm confidence that steadied the rest of the room. I hired him. I promoted him several times. When I asked what happened, he said he was traveling too much, was handed one impossible problem after another, most of them by me, and could not see where his career went next. The California trip I was proud of was on his list.
He had never complained. Not once, about any of it. I had taken his quiet demeanor as career satisfaction.
That is the part I still think about. My attention went where the noise was. The struggling technician, the escalated project, the customer who called me directly, all of them announced themselves and got hours of my week. The person carrying the most weight on my team never announced anything, so he got promotions and recognition and almost none of my time. Those are not the same thing, and I had been substituting one for the other for years.
I run it differently now. I deliberately spend time with people who are already producing, working on the things that hold them back rather than the things that are broken. Part of that is coaching. The larger part is that regular time with your best people is the only way to really understand what is going on with them. It compounds in a way that surprised me the first time I saw it, because a strong performer takes coaching and turns it into results almost immediately, while the same hours spent lower on the roster mostly produce adequacy.
That is a hard call to defend. Some people can be developed with attention and never will succeed without it, and choosing the top of the roster means choosing against them. I have made that trade knowingly. Losing an excellent person costs the team more than a struggling one ever does.
Your quietest employee is not your most satisfied one.