What purpose do seasons have if they're a very rough and completely inaccurate approximation of weather trends? Take Canada - or at least Toronto - jokes aside

What purpose do seasons have if they're a very rough and completely inaccurate approximation of weather trends? Take Canada - or at least Toronto - jokes aside about "winter season" and "construction season", or "cold weather" and "patio weather", the reality is there isn't much of a "spring" to talk about, it rarely lasts more than 2-3 weeks (and it's not uncommon having to switch from heating to AC within the same week, sometimes more than once). What purpose does the European model of four 3-month seasons have in other climates? You ask why. I think a better question is "why not"?