Nothing wrong with hours builders who instruct - mostly they are very highly motivated and committed to their career goals, good at instructing and they make a valuable contribution to the schools they work for. They are often a big loss when they do move on. As for some of the ones who'd like to move on but don't...... SOME of them end up making excellent CFIs and ATOs.
Who in their right mind would seriously think of instructing for a living.? It might be a lot of fun but there's no money or real career future in it, is there? If the instructing step helps get you where you want to go and you're prepared to commit to it, even for a short time, give it a go!