[desas]

The new builds are made of brick and block, and are indeed insulated really well. It's the millions of older houses, particularly Victorian ones, that are made of brick, are not usually insulated well, and are often intentionally draughty.

[Eavolution]

What would the reason for being intentionally draughty be? The only thing I can think of is if they were burning candles/gas lamps to improve air quality?

[neilalexander]

To reduce condensation and mould.

[albertgoeswoof]

Damp is worse than cold