No lol.

I know 21 °C is confortable for a room, no idea if it is even survivable in a pool.

I know I bake cookies at 350 °F, don't even know if it boils water.

As with most things, blame the Conservative government who stopped metrification a while ago.

Not at all, but due to the chart it "doesn't matter". We don't actually need to relate the temperature of the oven to the temperature of the house. Sure they're both temperatures of a volume of air, but they're not related temperatures. One is essentially just an abstract number you set an oven to without thinking about it. 350 for "cold", 400 for "medium", 425 for "hot", and the rest are whatever the box or recipe says.

I remember one day being like "wait, if 212 is boiling in American, what temperature is 350?" and being surprised that ovens get way less hot than I intuitively thought they did, but it didn't really matter, because it's just a number on the oven and nothing else.

Or, like, yeah I know my height in feet and inches, but given that I don't typically measure distances by laying down and using myself as a guide, it doesn't really matter that this isn't how I'd measure a room. Or I know my weight in pounds, but that doesn't help me weigh butter.

I'm not justifying it, I think it would be better if we switched more fully, but it's not as detrimental as you might think. Most people don't use the temperature of their pool, their own weight, and the length of a sheet of paper in the same formula very often.

As a Brit; take away thirty, divide by two. Really you'd only hear Fahrenheit temperatures on film or on TV programmes, so the accuracy loss is unimportant, and which can be mapped as:

• under 60 - coat weather
• 70s - t-shirt weather
• 80s - t-shirt and shorts weather
• 90s - dangerous heatwave that will make the news, have lots of fruity newspaper articles with pictures of people in their swims outside in the rivers, etc.