Because the correct English translation of «brevity is the soul of wit» is not the literal translation «la brevedad es el alma del ingenio», but 
«a buen entendedor pocas palabras bastan» . 

Bots with their millions of algorithms have no soul, no understanding, just a lot of information. As Chomsky said language is an infinite set of sentences. Therefore, machine translation is limited, both in the understanding of semantics and syntax, and that leads to errors in translation.