Personally i do not agree with this statement. This is because i think that, even though there are many examples of situations that would require good English and grammar skills, examples of this would be for an interview, or when writing a formal letter, there are more scenarios in which the English and grammatical skills used do not need to be perfect or used 'Correctly'
For instance, if someone is in an emergency, or a position in which they are in danger, then people would automatically aim to use as short, and quick words as possible., instead of long correctly spoken sentences. This would be in order to communicate the important information needed to help the person in danger faster. This is also used to an extent in the army, as they often use codes to inform people promptly immediately after any problems or dangers arise.
I also disagree with this statement, as if someone is having a conversation among people they know well, such as friends and family, they can be considerably less formal in their spoken language, than if they where talking to someone they did not know so well. This is because good English is associated with making a good first impression, almost making people feel judged if they do not talk correctly when not with new people, whereas people feel comfortable around their friends and family, and know that they wont be as judged by the way they speak, and as long as it is possible to understand it's okay. Another point is that when talking to children, its important to use simple short sentences so they understand you.
Also, the English people use can often differ depending on the area of which they have grown up in. Many places have a very distinct and particular way of using grammar and English. Sometimes even changing the way things are spelled or whole words altogether. One example of this is how people in America tend to spell the word colour as 'Color', leaving out the 'U', which is often used in the British spelling. Therefore you can't tell exactly what is the 'Correct' way of using English as it is different regarding the place and society that it is spoken and used.
This also links in to another point which is that if everyone spoke perfect and correct English all the time, then things like different accents would not exist, as everyone would sound the same. I believe that this would eventually become extremely boring, and it would be quite upsetting to get rid of some very distinctive accents. Especially accents that differentiate places in England, such as Liverpool or Newcastle accents.
My final reason for not agreeing with this statement is that being articulate all the time can often make you sound quite arrogant and almost egotistic. This can lead to people regarding you as conceited or pretentious when using it in situations or scenarios where it does not particularly need to be used.
