I don't do very much one-to-one coaching - my primary focus is on ensembles - but occasionally I'll do a few sessions with someone to help them along their way. Usually it is a friend of a friend who has found me by word of mouth and wants help with something that they find is getting in the way of their full enjoyment of a choral experience - typically vocal strain, tiredness or hoarseness by the end of rehearsal.
When I say yes to these requests, it's because of a combination of the personal connection, the fact they are usually able to come on a weekday afternoon when I am pretty flexible for time, and because I don't like the thought of people feeling uncomfortable in choir. It's not what choirs are for, and people should be going home feeling lit up, not hoarse.
But there's a specific pay-off I gain from these sessions: I learn a lot about how adults with some choral experience but no specific vocal training relate to their voices. A one-on-one session gives the chance for really close observation and listening as you work through vocal tasks. And this is useful because this is a profile of singer I meet all the time in my work with choirs.