Unfortunately, many Nigerian writers, some of whom are notable teachers of English Language, consider 'entreme end' and 'reason why' as tautological, by so doing misleading some learners. You may be flabbergasted to kwn that it is acceptable to say: the extreme end of the road - Cambridge International Dictionary, PP. 487 and Longman Dictionary of Contemporary English, PP. 481. More so, the 'reason why' I'm late is that I missed the Bus-Oxford Advanced learner's Dictionary. Note: reason is often followed by for, that or why.