That question is pretty common on forms I've seen here in the UK. As well as asking your race/ethnicity and religion. It's some "equal opportunities thing. I always answer with 'prefer not to say' as it's no ones business, and it's not compulsory for them to know.

This.

It's this kind of data collecting that got so many people killed in the war. The population registers at the Dutch town councils had a column for faith, making finding Jews very easy.

There are things better left unknown in the databases.