We may not be talking about the same thing. A linguist is one thing, a polyglot is another, and a translator is something else. Most linguists become polyglots in the course of their studies; some work as translators. But not all translators and not all polyglots are linguists. Being able to speak several languages makes you a polyglot, but not necessarily a qualified translator, nor a linguist.
Linguistics is a branch of Cultural Anthropology that studies the science of human language, especially looking for commonalities that enable us to quickly and efficiently learn a new language, analyze its phonological and grammatical structure, and compare those structures to those of other languages, to see what we can learn. Usually there is a practical motive for this exercise beyond the mere accumulation of knowledge, such as Bible translation in order to spread Christianity, or a government-sponosred program to develop previously ungovernable areas, whether for the benefit of the people (health, education, etc.) or for the benefit of the government, or both.
I was trained as a linguist. They dropped me off in a remote place in South America where I learned the previously unwritten local language, reduced it to written form, invented an alphabet for it, and developed a literacy program that enabled the locals to teach each other to read and write. I imported a mimeograph machine and a typewriter (computers were not yet available there at that time) and showed some friends how to produce an inexpensive newspaper in their own language.
After I left somebody else came and translated the Bible into that language, starting out where I had left off.
I just discovered last week that that Bible translation is now available for download on my iPhone. Unbelievable. I am going nuts reading the Bible in a South American dialect for which I developed an alphabet under fairly primitive conditions decades ago, on my iPhone.
Went to NYC last year and stumbled on a group of musicians in Central Park playing South American music in a dialect one province away from mine. We had a nice chat, partly in English, partly in Spanish, and partly in contiguous dialects of that native american language.