Technically, they weren't traps: they were tests, albeit ones that rewarded failure with death.
Given their elaborate nature, it's unlikely that Medieval knights would be responsible for their manufacture, and it is much more feasible that The Brotherhood of the Cruciform Sword are responsible, as Stefan has pointed out.
It's not the aim to make access impassible, but to allow only the Truly devout and Holy pass through, those who are worthy of the gift of God.
Only a Holy man would know the true name of God, and thus traverse
the stepping stones.
A Holy man would kneel in submission of the Lord, and avoid being decapitated by the blades.
A Holy man would have faith to trust in the Lord, and commit to the leap of faith.
Whilst these puzzles have relatively simple answers in retrospect, in prospect they require very specific knowledge and a very learned interpretation of the 'Clues' in order to decode.
They were likely crafted between 11th-13th Century (with enhancements possibly modified in the Interim), in a time when only scholars and the wealthy elite would have had access to the level of education to understand the Holy Passages; let alone interpret them accordingly, launch an expedition and find the site in the First place.
Considering the Crusades were 'waged' against Muslims and Heretics (in a time of Dogmatism), traps as simple as the spelling of 'The word of God' could even be interpreted as a deterrent to non-Christians; who would either not be educated enough to know the word of God, or more likely consider claiming the Name of the Lord to be anything other than Allah, Vāhigurū, (insert monotheistic Deity name) to be an act of Heresy.
If the Brotherhood of the Cruciform sword are responsible for the maintenance of the location, they could have modified the traps in keeping with modern developments (gramatically speaking), but considering the point in the tests is to reward those would would seek the cup, making the answer less obscure seems to defeat the purpose.
To step out of the narrative universe for a moment, it's most likely an oversight by the writing team. The idea of the tests fits nicely into the narrative, but the ramifications of centuries of change were perhaps not as thoroughly poured over as we might wish, but who can blame them?