I'm not sure where you've got this idea from. Even "new builds" in the UK, with there questionable building methods (which you may be referring to?) are mostly insulation and incredibly efficient to heat.

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.

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?

To reduce condensation and mould.

Damp is worse than cold

Resistive heating is still a big thing, including new products being developed.

Here's the latest: electric instant water heaters designed as drop-in replacements for gas boilers in hydronic heating systems: https://stromltd.com

All the inconveniences of a hydronic system and resistive electric in a single solution, what's not to like?

This is the perfect "slumlord special", installed in place of more economical (and ecological) solutions such as A/C knowing full well the tenant is going to pay the resulting astronomical bills.

Is naming the company in Danish (strøm means power) supposed to suggest Scandinavian efficiency?

AFAIK resistive electrical heating is banned in Denmark, except in buildings for only occasional use (summer house etc).

Incredible, downvoted to -4 for pointing out poor insulation.