A question about a comma

[Bassim]

I am just wondering why the author does not use a comma before the world "but" in the following sentences? They are from the book, "The Man who broke into Auschwitz",

1.My father had always taught me to respect people and animals but I was humiliated in front of all those men.
2.I had no real cover other than the night but he hadn’t seen me yet.
3.The seconds ticked by but he didn’t raise the alarm.
4.With the benefit of daylight and a bit of warmth we got the vehicle running again but before we got very far I heard the menacing sound of planes overhead.
5.It was dead men’s shoes in those days but the ordinary lads didn’t get a look in.

Is a comma in this sentences optional or is a comma in these places grammatically wrong?

[5jj]

Is a comma in this sentences optional or is a comma in these places grammatically wrong?

It's not a question of grammar, but of style. Most careful writers would use a comma before 'but' in all of your sentences, and add a few more commas in #4. Unfortunately for learners, there are few absolute rules about commas in English.