i always thought if you tow you got have Towing Mirrors i am beginning to wonder because i see alot with out them as well
The law only specifies what you should be able to see, it does not specify how you achieve it, so do you need extension mirrors if you have the required field of view with the tow vehicles normal mirrors, and the answer to that specific question is NO! But there other reasons why in 99.9 cases the answer is practically yes.
The legislation says you must be able to see the whole of both sides of the trailer when the outfit is dead straight from the driving position. For that reason the rear view mirrors (orpossibly camera's) have to be set wider than the trailer to achieve the requirement.
If the tow vehicles are not wider then the trailer, then the mirrors cannot see the whole sides of the trailer, then extension mirrors will almost certainly be needed.