I got it. Thanks so much!
It's true we English learners always pay too much attention to grammer rules, but as you know, most of us have little chance to communicate with native speakers frequently, so we don't know the way modern native speakers usually express themselves. Just as foreigners learning Chinese at home, if they don't talk with Chinese, they will not know what they learned from books have not been used by Chinese for a long time. If we, as you suggested, give up those grammar rules, we may speak and write English with Chinese sentence structures, which will be more difficult for you foreigners to understand. Don't you think so? So, please understand.