Lol a couple of points since I assume we living in same country: (i) singles can but new HDB with parents, can buy if unmarried but have kids (but need to file some approvals separately; (ii) all single individuals (including both unmarried and widowed with no kids) cannot but HDB or HDB resale until they are 35. So from these two you can tell that the criteria is not about gender preference, but whether you have kids.

Secondly you clearly do not understand the concept of subsidised housing. They can go buy condo and private property all they want, but if they want to pay a subsidised pricing for housing, they will be subject to criterias. My unmarried friends have to live with parents till 30s, and he understand that’s fair because he don’t want to spend on private housing. Your assumption that everyone is entitled to a large, heavily subsidised housing by the gov is just wrong. If you want to pay market price to buy private property you can buy however you want with no restrictions.