Singkies houses too small, that's why need to go outside to have sex. Not like merehsians, can do it from upstairs to downstairs, from kitchen to bathroom to living room to porch, to backyard/sideyard etc.

Singkies homes so small, somemore a lot of them rent their hdb rooms to outsiders, tak ade privacy at home so do it outside. Pitiful.

That is also one of the possible reasons, but not entirely true.
Waifu and I also find it exciting to do it in public, but we've only done it once, because when you have a comfy home, you wouldn't really be so motivated to do it in public.

Singkies having small homes, and many of them renting out their rooms to outsiders is a known fact, so comfort and privacy at home are the main issues. I believe this is the main reason driving them to have sex in public.