Because I actually tried, for the Italian translation.
The fact is, due to cultural and societal differences, with different languages there seems to be different preferred quotes, even from the same author. Add to this that even after tens of years of digital data, english language is still the lingua franca of the net, and you'll find that's very hard to google for foreign translations of less known quotes. You may have a chance if you know from which book it comes from, but then again, that information is not usually passed along with the quote and a translated book may not exist at all.
Hence you have to rely on your own translation, which maybe is fine, mind you, just perhaps not the best.
Source of the post
And you think professional translators will somehow eliminate the inherent ambiguities between languages?
Not at all.
I just wanted to publish a quote, that's all.
As it happens, for those who don't know, it's one of the most famous quotes of the entire Italian literature, the last verse of the first book of the Divine Comedy.
I googled for translations in three foreign languages. Of course different translators made different stylistic choices, no problem with that, yet I've been able to find only two translations per language in half an hour. One of them just because the no more existing domain was cloned under archive.org
For other authors, I've not been so lucky.
Anyway, I'm not saying I'm against personal translations, only that if you all want to cite less known works, try to add book references as well. After all it's customary in citations.