There are implications by linguistics. If you learn a language you also passively obtain insight into cultural norms and expectations. Moreover, Learning a language is much easier if you're friends with natives and converse with them on a semi-regular basis. Being able to speak the language also means that there doesn't need to be a separate support structure for you, as you will be able to use the ones provided to everyone else.

I'd wager the sum of these things is something one may expect from a permanent resident (i.e.: cultural knowledge, some amount of integration, ability to function without specialized support structures). And it turns out, that language proficiency is a pretty good proxy for measuring that. Just because you don't accept the rationale behind the requirement it does not mean that there is none.

The requirements are not there to verify that you can live somewhere permanently, but if you _may_ live there permanently. Money is not the only dimension your so called "net positive" may be measured in.