There is a lot of anger directed at markers here and while I think that exams can be deeply unfair, it's not entirely fair to pin all of the blame onto the people that mark exam scripts. One of my family members marked exam scripts last year and even though it was for maths (where you would expect marking to be super easy, since it's not essay-based!), markers don't get very much support at all. It's usually just the marker (who may have never done this before) and a very, very vague (and sometimes even incorrect mark scheme). Within about 2 weeks of marking, the mark scheme had changed about 4 times because there were so many errors in it.
And sometimes it's not even the people marking it, sometimes the mark scheme is just stupid. For instance, the exam question required you to measure a line and state how long it was in cm/mm. For 2 marks, the correct answer was 8cm or 8mm. You got 1 mark if you were within 0.5mm of this figure on either side i.e. within 7.5-8.5cm. The dumb thing was that you got NO marks whatsoever if you just put 8. That's really dumb in my opinion, penalising someone that much for forgetting to put units, even though they measured whatever it was correctly.