I disagree with "StoneyB on hiatus". Everything has a reason. It so happens that the reason is no longer relevant, but the rule is preserved according to tradition. However, still, the reason originally was.
In the past, there were grammatical cases in English, but now they have almost completely disappeared. In languages that have cases, they show what function a word performs in a sentence. For example, you can understand who is acting towards whom. Thanks to the cases, the word order can be free, unlike in English. But if you ask a native speaker, what is the purpose of the cases, he may also say that this is just such a rule, because he has never thought about the reasons.
English cases are no longer used because they are no longer needed. Everything that has survived is probably used for something.
"mobileink" made a good comparison with evolution. If we consider the human body as a result of evolution, it was not specially designed. However, there is nothing superfluous in it. In the past, it was believed that some parts or organs were no longer needed and, for example, could be cut out. And then it turned out that they did have a function.
If an agreement exists, it most likely serves some function. The function of such things is usually to provide information that is necessary for a correct understanding of a sentence.
Yellow Sky gave a good answer.
StoneyB on hiatus said:
Thou run'st, he runneth, and we/ye/they runnen (if you go back say 600
There are no longer so many agreements. But since some remained, perhaps they are necessary for something and have some purpose. What is not needed is gone, what is needed is left.
Interestingly, English is still partly a pro-drop language.
English is not a pro-drop language. Nonetheless, subject pronouns are
almost always dropped in imperative sentences (e.g., Come here), with
the subject "you" understood or communicated non-verbally. Wikipedia
For example, the imperative sentences have no subject pronoun:
Pass the salt.
Move out of my way!
Shut the front door.
my leather jacket.
Be there at five.
Clean your room.
Use oil in the
Stop feeding the dog from the table. (Request or
The examples are taken from yourdictionary.com
"You" are implied, but not said.
Could it be that since the verb does not change, but looks like in the present simple tense with "you", it is clear that there is an appeal to the second person?
I cannot understand if imperative sentences have any tense. But if we consider "Pass the salt" in the present simple tense it will be:
I pass the salt.
You pass the salt.
He passes the salt.
It is possible that the verb's change in the third person still exists so that there is no confusion whom imperative sentences are addressed to?
There can be no confusion with the first person because a person cannot address himself. There can only be confusion with a third person.
Thus, it is unambiguously clear that when an imperative sentence without a subject pronoun is used, the appeal is to "you", and not to someone else. That it is "you" who should pass the salt, and not someone else. Misunderstandings are ruled out since there is no "-es".
This is not all.
In informal speech, the pronominal subject is sometimes dropped. This
ellipsis has been called "conversational deletion" and "left-edge
deletion", and is common in informal spoken English as
well as certain registers of written English, notably diaries.
Most commonly, it is the first person singular subject which is
Let's take a look at examples of the conversational deletion from learnenglishwithdemi.wordpress.com:
Gotta go now. (I gotta go now.)
See you later. (I’ll see you later.)
Got a minute? (Have you got a minute?)
Mind if I sit here? (Do you mind if I sit here?)
See what I mean? (Do you see what I mean?)
Wanna ride? (Do you want a ride?)
Hope this lesson … (I hope this lesson …)
Got any questions? (Have you got any questions?)
A little more of Wikipedia:
In speech, when pronouns are not dropped, they are more often reduced
than other words in an utterance.
Relative pronouns, provided they are not the subject, are often
dropped in short restrictive clauses: That's the man [whom] I saw.
As a conclusion from all that has been said:
In my opinion, the remaining Subject-Verb agreement in English can serve for avoiding confusion/misunderstanding and restoring the subject in the addressee's mind, if the subject has been omitted. It's like backing up the subject data in a verb.