He does this in order to keep his job (which he loves) and to avoid any judgment from the uber-conservative townspeople. Tom is an interesting and sometimes depressing character. Despite his love for his students, he is very unhappy and only seems to come to life when he takes his irregular trips into the city for one night stands. It should be noted that Tom has good reasons to be as closed off as he is so watching him slowly come out of his shell throughout the book is a satisfying experience.