[youraverageuser]

Probably because it is very easy to mess up when using state incorrectly. It has been years since the last time my program run without bugs for the first time. If you're a genius, then sure, whatever tool you may be using, you'll do fine. But I noticed that many mainstream programming languages introduce concepts that are easy to misuse, even the same global variables. I recently wrote a small python script in 40-50, having concise and separate functions, etc. And I still was stuck on a bug that turned out be a consequence of shared state. The real issue was far from the location I was observing the bug. I think those kind of bugs is quite common.

What it boils down to in the end, is your priorities. If you want a program that works 90% of the time and you don't care about the last 10%, then sure, stating your way through is quite natural. If you're sick of the small bugs that is the consequence of the language semantics and not the logic or design, then you'll start nailing down the factors that contribute to the erroneous nature, with state being just one part of it.

Based on my experience in python and trying to teach other python developers some fp (spoiler, it didn't work)