It’s missing the semicolon but it doesn’t necessarily know where you want it. Like a missing parenthesis etc. how does the machine know where you want it? If it could do that- why would you need a programmer if the machine can program itself? But let’s say it adds a semicolon where it thinks you want one and doesn’t tell you. If your code doesn’t work- how do you know why? You’ll still have to go through it and find the bug. This defeating the purpose of it telling you there is a syntax error etc. to start- being to help you find the bugs before you compile and having to go line by line or debug to figure it out. In other words the sentence I just wrote is missing punctuation So- as a rule we know at least it is missing a period. We could but if it isn’t human readable, how do you know the first sentence ends at the word “punctuation” and not “So”?
Well... “So” is capitalized. But... proper nouns are capitalized too. If you just add periods to the word before any capital letter that doesn’t work does it? My fiend calls this “obvious. See that? Missing parenthesis. We know there needs to be another one. Brackets need 2 as well in most languages. So if you see ( and the next parenthesis you see is another (- you know there is an error in the code for most languages. Computer can tell you simple stuff. Computers generally require a humans judgment for anything that requires a non absolute determination.
Now- long ago kids, you wrote in Pure Binary, Assembly. These are some true machine languages and NOTHING is taken care of for you. Writing modern programs in these languages is, in some cases, impossible for one or even a small team of humans. In general it isn’t practical. So we get higher level languages and newer syntaxes and portable code that does black box magic behind the curtain. Someday- we may have 100% human language programming where you simply tell the machine in relatively plain but proper English (or whatever) what you want done and the machine figures out how to do it. Someday. And then we likely won’t need programmers any more. Or will all but not need them. Until then- be happy it’s gotten much easier to code and you aren’t doing things the “old fashioned way.”
TLDR: You don't want the computer to fix errors for you, because what if it fixes them incorrectly?