The bottom end is much harder to justify but I believe the idea was that you wouldn't have to regularly deal with negative numbers.
But both F and C are completely arbitrary. That's the least messed up part of the non-SI unit system.
0°C: cold, 100°C: dead
0°K: dead, 100°K: dead
< 300 K: cold
> 300 K: hot
Let's switch to Kelvins
The original idea of Farenheit was that 0-100 was the range between the freezing point of salt water and human body temperature, and it was designed to be convenient for use in labs. At the time, 0F was the coldest temperature you could reliably make in a lab environment (using a saltwater ice bath). 100F was when the thing started to be uncomfortable to touch, I guess?
Sure, as an American living in the northeast, it is pretty convenient for my current use - temperatures vary from 0 (sometimes below) to a little less than 100 over the year and I know what "jacket weather" is - but that doesn't really mean anything if you don't live in this exact climate. I imagine that if we switched to Celsius tomorrow, after re-learning the numbers for "put on a sweater" and "put on a jacket," it would be about the same.
“Uncomfortable to touch” heavily depends on thermal capacity (how much heat there is in the object to touch) and thermal conductivity (how fast the object can get that heat into your skin), so I would think defining that exact point to be quite the challenge.
As to the Fahrenheit scale, it’s worse. https://en.wikipedia.org/wiki/Fahrenheit:
“The other limit established was his best estimate of the average human body temperature, originally set at 90 °F, then 96 °F (about 2.6 °F less than the modern value due to a later redefinition of the scale)”
So, Fahrenheit arbitrarily picked 100 °F as some distance above the point for average human body temperature, changed it to 96 °F, and the scale was later redefined.
And still people claim that scale is less arbitrary than Celsius, Kelvin, Réaumur, etc.