> slovaks living in cz never learn czech,
Not entirely true, just "somewhat". You apparently don't know enough of those who do, because they hide in plain sight.
> czechs learn slovak to understand them
So far I met only 1 Czech who learned Slovak lang "just because".
The important thing there is "why if this already works for me?".
But indeed, this is an interesting topic to dissect. What I find interesting is how the two societies think the languages are very close, but outsiders (e.g., Polish, or Croats) would mightily disagree (typically understanding one easily (typically SVK), but not the other (typically CZE)).
I just had this discussion yesterday: listening to Ukrainian, I get most of what they say without translation, but it just doesn't work the other way round (recent anecdotal experiences from conversations with Ukr refugees).
Both of the languages are artificial to a large extent, with a shared base. e.g. Polish is difficult for me to understand, ukrainian is about the same. Russian seems to be still one level further
> you pick up words and phrases and grammar quirks from coworkers etc and then mix the languages
Which becomes hilarious when you mix a e.g., grammar of a Slavic language with vocabulary from a Germanic language, of course declinated according to that Slavic grammar! We speak a lot that way in my family 😄 .
Even more, my children would write one language with orthography from another language, which makes for a very cryptic stuff.
Yes, mixing languages is fun.
