Of course there are exceptions, but to the native speaker everything is just natural and "hard to explain why it is like that...". Whereas a foreign person who has learnt the language himself is more aware of what the challenges and confusing bits are.
That's true. I've always been interested in Russian language, but on this forum I sometimes find things which are difficult for me to explain. I could not imagin that, say, verbs of motion are so difficult.
Although texbooks are written by people whose profession is "Russian as a foreign language" and who have long experiance of teaching Russian to foreigners.