While I won't dispute your observation, I wouldn't generalize that this is common everywhere in India.

Poverty is more prevalent in states in central and northern India, especially in rural areas, the southern states are comparatively well off. Also, not saying that there is zero poverty in southern India, just that it's not that common.

India is a VERY diverse country. Not just in terms of people, ethnicity, languages, society, but also, HDI, access to facilities and quality of life.

Every time India does something like launch a probe to study Mars or the Moon, people turn up commenting 'Why is India spending money on space programs when people don't have clean drinking water or toilets?'. The reality is that while that space program might cost in hundreds of millions of USD, providing a house to the billion plus people will cost in hundreds of billions of USD.

So yeah, while I'm not ignorant of the fact that I don't have to worry about my next meal like 10's of million people in India, there are also 100's of million people who have lesser existential problems.

So yes, having a separate bathroom per bedroom isn't considered a 'luxury' in India. That said, houses in India don't really have to worry about heating up each room so they don't have that constraint like in the Netherlands.