45 languages * 44 other langues ~= 2000 translation directions. There are ~4,500 languages with more than 1,000 speakers ~4,500 * 4,499 ~= 20,254,500 language pairs so that's a very long way from every language.
Frankly though, I imagine the vast majority of those languages are unappealing targets in terms of return on investment.
and much smaller training data..
I guess they really don't need to cover all of them though as most of the people speaking a language with low number of speakers would be able to converse in other mainstream languages as well. I can speak four languages but I rarely converse in two of them as speakers of the two languages are usually comfortable with a mainstream language as well.
Even Swedish is barely in the top 100 with 8.7 million speakers.
The most obvious thing to me is to use an intermediate language - I assume this has already been discussed extensively, anyone have references?