DD decided when she was about 20 that she was too uncompromising to sustain a relationship or be a mother.
She has lived happily alone, now, for nearly 30 years. She is a happy and sociable person, but family are the only people who visit or stay with her. We are always welcome.
We had to nurse her for several months after a serious accident and found after the first few fraught weeks, that she was happiest to only have one of us with her at a time.
I can see no reason why anyone should have to defend a decision to live alone. In many ways I am like DD. For most of my (happily) married life, I had a DH who travelled a lot, so I frequently found myself alone, for days, week and on several occasions, months, and was as happy as Larry. If/when I become a widow, I will happily live alone for the rest of my life.