It’s English, English is a descriptive language meaning that however it is used is the correct way. If you want a language that has strict rules as to what is and isn’t correct please see french.

The “rules” you have been taught are only guidelines for the period of time and location you were taught them in. For example I was never taught to use <> as quote marks it was either ‘ or “ but obviously you were, we are both correct because I understood you perfectly.