Why do authors say "have to"?

Part of the problem with English is that many words are from other languages so that creates confusing inconsistencies. I won't dwell on that here but I can understand the confusion.

I don't think the issue is only related to the primary or secondary language but it's also related to the grammar of the language, English grammar is bit confusing not bit but very confusing.

Thank you, Mahesh. I do understand that it is difficult to get every detail correct when a person is using a language that is not their native language. I wanted to ensure I did not miss something.

I seldom see spelling errors. I assume authors are using the spell checker or a spell checker. And see, that is one thing that makes English confusing; the logical term is "spelling checker" but for some reason people usually say "spell checker". I think it is possible to implement a simple grammar checker. We cannot check for everything but at the other end of the scale there are a few things that could be checked for. There are some things that could be identified as possible corrections.

I do see authors doing better at using the grammar that I use. Doing it my way is not the important part; the important part is that they are trying to write well.