I think the basic reason is that the "Jewish translations" (into English, anyways) are fairly recent, historically. (I'm sure BananaBrain will correct when I go astray..)
To understand the Torah, it's taught in Hebrew - no need to translate - to study it, you learnt Biblical Hebrew. (As you would for the rest of the 'Old Testament' - the histories, prophets & psalms) To study the commentaries, you'd use Hebrew or Aramaic (I think - I have enough trouble transliterating Hebrew & haven't gotten into it in depth) - because that's what they were written in. You want to study it, learn the language.
That's been less the case in Christianity, which has used Latin as a sacred language for most of its existence. Therefore, translations of the Hebrew scripture were needed - primarily into Latin. When the Protestant idea of studying the Bible *yourself* rather than the Catholic/Orthodox version of relying on a learned intermediary caught on, the translations started into all the other languages.
More recently, Judaism has started to move (in some groups) away from the emphasis on needing to know Hebrew to read the Torah, and more translations have arisen. I may be wrong, but I think it is a very modern (relatively - late 1800s CE on?) phenomenon. Since the more recent translations (e.g. JPS) have been direct (versus some of the Christian versions which came via the Latin Vulgate), they're possibly more accurate.
And to add to the mix, which books are *in* the set differ as well - Torah is Torah, but some of the other books differ between Christian groups. AFAIK there's not a batch of worries in Judaism about what's Apocryphia or not.