Certainly more of a problem for diesel cars (diesel starts to gel not much below freezing). However, if there's any level of condensation in your gasoline tank you do have to worry about the fuel lines developing ice crystals... I wouldn't like to bet my life on starting an off-the-shelf car without any preheaters in -40 degrees

I went down a small youtube rabbit hole one night. There are some youtube channels showing guys getting up at the crack of dawn and starting their cold engine diesel engines without block heaters.

It seems if you are sufficiently prepared they are not needed.

It's true that just about any modern vehicle with a quality battery will start in -40°F , but oil distribution will be suboptimal and you'll put strain in cold, brittle places it shouldn't be. I guess 'need' is a strong word, but every time you start a vehicle in that kind of cold you do a tiny bit of damage to it. Keeping it a little warm during startup is really important for long term health.