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Controversial Opinion: Constitution is a surprisingly good dump stat
It takes 9 Constitution points to go from 7 to 16, which is the most you can benefit from in most classes.
Those 9 points only get you 2 hp per level.
You can do so many things with those 9 points.
If you're a mage your protections will make HP a moot point most of the time anyway. Thieves are gonna want to make a hasty retreat if they end up in the line of fire most of the time. Clerics have a level 2 spell that will eventually be able to boost their constitution by up to 6 points. Theives probably rely on their constitution the most but they all to various degrees can afford to lose some Con points.