Adults do learn languages well when required, sure. I question that we should. Making additional [1] billions of people learn a new language is not cost-effective compared to a (comparably) small number of software engineers wrestling with i18n (haha). It is sad that English knowledge is very valued among, for example, several non-English [EDIT] workplaces even when it is not required at all.
> Hangul would also be a nice lingua franca writing system, too bad its very local
By the way, Hangul was tailor made for Korean with its relatively simple CGVC syllable structure. I doubt it can be generalized much---Hangul is important because it is one of the first featural alphabets, not because it is a universal (or at least adaptable) featural alphabet where it isn't.
[1] English has about 2 billion speakers (400M native + 750M L2 + 700M foreign), so you need another billion speakers or two to make your proposal real.
[EDIT] was "CJK", but I'm not sure about Chinese and Japanese.
Instead of the total number of speakers the better metric would be the diversity of the speakers.
A language is a better candidate for a lingua franca if its spoken everywhere a little, than somewhere a lot, e.g. Mandarin.
And this is not about cost, but about Bugs in critical infrastructure.
I'd get rid of smartphones and unicode in a heartbeat if it meant bug free command line applications, no malware, and medical and infrastructure that doesn't crash.
I think its great when non english workplaces require english. It gives people an incentive, because humans are a lazy species. And once you learned it you can use it on your next vacation, your next online encounter, and who knows where.
Having computers only do english would have given a similar incentive, and I'm sad we didn't use that opportunity.
> Hangul would also be a nice lingua franca writing system, too bad its very local
By the way, Hangul was tailor made for Korean with its relatively simple CGVC syllable structure. I doubt it can be generalized much---Hangul is important because it is one of the first featural alphabets, not because it is a universal (or at least adaptable) featural alphabet where it isn't.
[1] English has about 2 billion speakers (400M native + 750M L2 + 700M foreign), so you need another billion speakers or two to make your proposal real.
[EDIT] was "CJK", but I'm not sure about Chinese and Japanese.