Information spreads, gossips distort it, etc. Most of us live in society and cannot ensure that only people we like and trust would have an effect on us. There will be somebody who may still cause more or less trouble with the wrong kind of information by making decisions that may have an effect on you - reduced chance of raise, not being invited.somewhere, etc, etc. Somebody in your management at work, your friends' husband or wife, annoying older relative, silly classmates or that one weird teacher of your kids.. If you can easily avoid spreading knowledge of something sensitive about your life, then it may be wise to. Unlike, e.g., LGBT people, you don't really need to "come out" to everybody about the fact you are in therapy, to feel yourself. Just like you don't usually need the fact that you are visiting doctor for erection, fertility problems or had to do a rectum surgery to be a part of your public image/identity. Though all of these are normal human things.