what others have said: if they cant read it they cant mark it
examiners have to read through a tonne of exam papers every single day when marking them, and i can promise you a lot of those have terrible handwriting because its an exam and people are going to be writing quickly
heres the easiest way to describe it: you wont get marked down if your writing isnt perfectly spaced or sized, but you will if you literally scribbled all over the page for an hour and then handed that in. bad handwriting doesnt get marked down, but they need to at least have some idea of what the words are meant to be