Mercule
Adventurer
It also takes players who care about the "benefits" brought be splitting the languages.I don't disagree with this, but...
If you're assuming a skilled (or experienced) DM to fix this issue, what do different languages bring to the table? That same skilled DM will be able to deal with it even if everything speaks Common, while a non-skilled DM is liable to have problems even with a wide range of languages.
My degree is political science, philosophy, and history. I now work in IT. My players have degrees that include computer science, animal ecology, and English. They work in IT, food service, and labor. Trust me when I say that there are certain things that I find interesting and am skilled at bringing into a game that have no overlap with what my players are interested in.
I used to split out languages and make the regional customs important for certain scenarios. Some players really took to it, which was great. Others just found it baffling. In the end, the small pleasure I thought I'd get out of splitting languages wasn't realized and ended up being a detriment. I still do small variances in regional culture and lore (which makes the foreigner sometimes very valuable), and I have different "common" tongues for different continents/sub-continents, but it's more along the lines of European, Asian, Indian, Iberian, Middle-Eastern -- if that. Within a given Common tongue, there are going to be accents that give away birth/nationality, but that's about it.