I get a little bit annoyed when I hear people talking about coaches or trainers that 'must not be good' because they 'use a trainer themselves'. They use them because trainers and coaches understand the importance and value of having that person there.
Take motivation, for example. People hire a trainer for accountability and to give them a push. Trainers are people too. Yes, they're very good at pushing others but finding your own personal motivation is a very different story.
Subjectivity is another thing. A lot of us generally have a slightly messed up vision of ourselves. Mirrors and photos tell lies and that’s before we get into our feelings and emotions towards our own body. Having another person there that you trust to give you honest feedback can allow for the correct realignment of that vison, not to mention help with the proper regiment of nutrition and exercise. For example, lots of people panic and think they're not lean enough and then over-diet.
Accountability, motivation and subjectivity aside, it can also just help to have that 2nd opinion. Everybody I've ever met has a slightly different approach. Spending time with a good trainer can lead to new ideas and knowledge, even if you're working on the plan of action together. It can also help reduce worry and anxiety.
I hope that people can look at trainers and coaches being trained by other trainers and coaches as a positive ‘experience by association’ type of thing e.g. in the situation where someone wins a junior competition and was trained by an ex-national champion. I also hope trainers don't think just because they theoretically know what to do that it's unacceptable to hire a coach yourself. Most of the best sportspeople, competitors and champions do.