Updated Mar 15, 2018
One of my general, default assumptions in life is that, most people I meet will spend very little time or energy thinking about me. They have their own lives to think about.
Also, when some person forms an opinion of me, it is important to distinguish whether or not I should care.
Anyway, my answer to the question is that, there seems to be a pattern of condescension, with women being worse than men.
You must be financially impoverished and pathetic. Underneath the pretense of sympathy, your lack of possessions helps them to feel wealthier than you, and thus superior.
They may deride your housing choices, assuming that a modest studio apartment is automatically a filthy hovel (even if they haven’t actually seen it).
On the other hand, they may view you as being “cheap” and refusing to spend enough money to enjoy life (by buying stuff).
A female-biased issue is clothing. Women compete on this all the time, and a woman with a minimalist wardrobe (plus simple hair and zero makeup) may be openly sneered at, like she is too stupid to know how to dress properly.
You may be viewed as somehow “not” really an adult, due to your childish refusal to accumulate an adult-sized pile of stuff (and debt).
If you show any level of geographic mobility whatsoever, the “not”-really-an-adult thing gets even worse, and you may even be ordered to “settle down” by someone you have just met. This is another one that is highly female-biased (men don’t care).
Yet another female-biased “not”-really-an-adult point of hostility is if your personal minimalism includes being single and childfree, especially if you are over age thirty, and are satisfied with your situation.
Like many areas of life, it is based on competition, and people taking personal offense, as if the “different” individual somehow owes them validation, and is maliciously refusing to provide it.