True, we should be using a temperature scale that was defined on how cold it was in Gdańsk, Poland in the winter of 1708, something the average man is more familiar with than water temperature, right?

The fact that 99.5% of the global population uses it makes it the objectively correct choice.

The remaining .5% can keep bashing their heads against a wall if they like though

We used water to decide a lot of measurements. 1ml of water is = 1 gram. A gram of water is also equal to 1 cm^3. It's a beautiful system in that way. Water surrounds us and gives us life, it has chemically interesting properties that make this planet function. Why shouldn't we just base everything off of this one substance?

When it's "freezing cold" or "ice cold" outside, what do you think is freezing? When something is "boiling hot", what is boiling exactly?

We use water to describe temperature even without using Celsius, because it's everywhere around us, and we are literally made of this stuff. It's also one of the only materials that goes through three different states in our usual temperature range, so using those as a reference point to measure temperature makes perfect sense imo.

Maybe ecause everyone uses it? Just so you know nobody even knows how fahrenhiet was defined first, everyone in the scientific community uses kelvin which is celsius but shifted so absolute zero is zero on it and the us actually uses si they just convert it to imperial so conversion between them is easier. There is point to imperial units other than its hard to switch between systems.

You can get used to any scale

The temperature of water is very intuitive in nature. Dip ur hand in ice water. That's almost 0C. Dip ur finger in boiling water (very quickly). That's 100C. Dip ur finger in coffee whose temperature is fit for consumption: that's around 75-80C. Ur hot water shower is likely between 37 and 41C..

Everything is tied quite well to water. Now compare that to F. What's 0F? What's 100F?

Forget the intuitiveness of celsius. It's also much easier to calculate using celsius. When I say "My coffee was worth 80 calories", I'm referring to a measure called "KCal", which is the amount of energy required to raise the temperature of 1 litre, or 1 Kg of water by 1C. So if u ate something worth 100Kcal, you consumed enough energy to heat 1L/1Kg of water from 0C (ice) to 100C (steam). The average human requires around 2500 KCal everyday. Which is equivalent to 2.5 liters of water. Pretty cool, huh....

Just a quick sidenote: KCal is still not an "SI" unit. "Joules" are what we use here, but that's another story.