Many older transwomen chose to transition in stealth and for good reason: society wasn’t ready for them back then and the backlash would have been dramatic. Because of this early transition, many were spared the effects of prolonged testosterone exposure which means that they were able to blend seamlessly into society and, in some cases, even marry men who knew nothing of their history.
Today this is virtually impossible, but we do have situations where many of us can pass for genetic females and have some people know and others not. When we meet new people, we must decide to what extent we want them to know our history especially if they are not close friends. There is no simple answer here.
I do not think that our decision not to tell is about deception but rather our natural desire to protect ourselves from the prejudice we are used to hearing about all our lives. Our impetus to fit in and be accepted on the merits of more than our gender is what is behind our hesitation.
As my life as Joanna has expanded itself I have been faced with this dilemma and I will continue to take things as they come and decide on a case by case basis what I will do.