This isn't obvious to people who haven't been in that situation and it's a phenomenon that deserves more attention.
What's more, you're completely full of it, if you're suggesting that this level of ease is normal. The people I've met that know 8 or more languages, all had to put in a substantial amount of time doing, time which they didn't have available for other tasks.
The first time that I personally encountered this was at Starbucks in China, where I couldn't decide whether to use English or Chinese and was barely able to blurt out comprehensible words in either language.
As for the 1st world, what does that have to do with anything? Part of the reason why the 1st world is the 1st world is the efficiencies inherent at being able to conduct business in just one language. The time it took you to learn those extra languages didn't just get spontaneously generated, you made choices to use your time in that fashion. In the 1st world, we generally use that time and energy on school and work.