Why people attend college? Is there a grammatical error in this sentence?

There are grammatical errors. The interrogative word is at the beginning of the sentence, and must be followed by a question sentence pattern, just like the train carriage must be dragged behind the locomotive, and a bus or truck will never be towed, otherwise there will be problems such as being unable to tow or derailing. , here the question word is placed at the beginning of the sentence, and must be followed by a question sentence pattern. Birds of a feather flock together, that is to say, the verb must be placed in front of the subject. Attend is a general verb and cannot be directly placed in front of the subject. An auxiliary verb do must be added. , after placing it in front of the subject, the following general verb attend uses the base form. If the question word is followed by the word order of a declarative sentence without an auxiliary verb, that is, the word order of the sentence you just gave, then it is not an independent sentence, but a subordinate clause in a subject-slave compound sentence, also called a dependent clause. . For example:

I don't know why people attend college.

I hope I can help you clear up your doubts.