Possibly it's to do with the chance of them putting pressure on you or something? Or it becoming a "thing"?
Sometimes I keep my constructive stuff on the down-low for that reason.
I, too, had assumed that to be the reason at first. My life, prior to my death, was genuinely catastrophic in almost every way that a 'first-worlder incel life' can be. Of course, at that time I hadn't actually
known I was an incel, but I still was affected by many of the things that incels suffer through regularly (which is also why I disagree that incels can't be under eighteen). I won't go too into detail about said suffering, but the only relevant thing that needs to be noted for this particular topic is that I was
incredibly prone to procrastinating and underachievement. At one point, every waking day was spent failing and losing at one thing or another—whether it be my grades, my sad attempts to fit in which I called 'hobbies,' or some other aspect of one's life within his adolescence.
A lot of that actually can be attributed to low IQ, which I wasn't aware that I possessed at the time, but that's off-topic...
Regardles, my family witnessed my constant failure, and the disappointment and embarrassment that I went through was humiliating. So, moving to the present, I naturally assumed that I must be hesitant to let my family know I'm doing anything because I intrinsically fear being held to some standard and failing at it again.
But, the more thought I gave it, the more I realized that wasn't the case at all. There's just something about sharing any achivement that makes me feel... wrong...
When I say that 'only the Dark raised and loved me, and therefore only the Dark should see me prosper,' I literally mean that as my main justification. I wish for almost nothing more than to be an enigma that nobody knows anything about aside the very surface of what I present—like my name or apperance. If my family would think of me as nobody special or relevant, I would be happy and relieved. I don't want to betray the Darkness who raised me and molded me into who I am today...
It's actually rather strange, I'd describe myself as an extrovert, and yet I desire to keep to myself in such a tenebrous and ambigious way...