Because mastering the native tongue shows the programmer was able to learn a lot of important basics at a very young age. Whereas the inability to master the native tongue shows a lack of education.
> able to learn a lot of important basics at a very young age
Ok, and why is that important? Could be a ton of reasons why people are lagging behind when they are younger but be able to catch up when they are adults. Judging people based on how you think they might have been when they were younger feels... Not fair. Judge them based on their current knowledge and person instead.
> inability to master the native tongue shows a lack of education
I think you're reading too much into it. Education has nothing to do with native tongue. People forget language.
I myself speak my native tongue a lot worse now when I lived outside the country I was born in a couple of years. Does this mean I lack education? No! I do lack any education, but that's not the reason my native tongue is getting worse every passing year.
One can master owns native language being an adult, why not?
I am Russian and I enjoy translating wonderfully sounding English concepts to Russian. As you can understand, it takes a little bit of mastery in both languages. The upside I get is that these wonderfully sounding language concepts often lose all their charm when translated into Russian. They turn into a pumpkin. This way I can better focus on what is essential.
Let me quote: "They're perfectly justified: the majority of hot new whatevers do turn out to be a waste of time, and eventually go away. By delaying learning VRML, I avoided having to learn it at all."
Another upside of translating things is that you often cannot apply same questions to English and Russian terms. There are questions applicable only to English term and there are questions for Russian term which are not applicable to English one. You have to do analysis anew, finding new sides of the problem, which either show you the problem's true underwater size or help you solve it.
Because learning a formal language is akin to learning a programming language.
You misunderstood education as formal education. Just by exploring as a child, and living, you learn your native language. Before a child goes to school, they already learn by playing. That, too, is education, and sadly some children are deprived from that or their lack of intelligence already shows. Our oldest (not even 3), for example, is well ahead language-wise, whereas motor skills she's a tad behind.
If you don't practice something, the skill tend to get lost, yes. However, something you learned at a very young age defines you, and is (for good or bad) difficult to unlearn. Only at an old age or due to memory/brain related disease does it get lost.
When I went on vacation to USA for 3 months, twice, I had to speak English. I didn't speak Dutch at all. When I got back, I had to adapt to Dutch way of living and Dutch language, but it went rather quick. I have no problem 'thinking' in English because I learned this at a very young age; whereas French just never clicked with me.
These people who end up with expat parents and the like are an exception. Exceptions like these prove the rule.
