Towing without mirrors

I know I'm new to caravanning (so probably still paranoid when driving with the caravan behind me) - but why do so many people tow without extension mirrors - I've recently returned from a festival over the Bank Holiday weekend, and have to say that at least two thirds of the caravans that I saw didn't have extension mirrors on, and when they pulled in having overtaken me, I could easily see that their car mirrors weren't wide enough to see down the caravan sides.  And most of them couldn't see through the caravan either (not that that excuses not having the mirrors).

I know setting up the mirrors is a hassle (I never seem to get mine in the same position), but I couldn't live without mine and I have an old van that is only just wide enough to make them a legal requirement, and I can see straight through the van if i open the front and rear curtains (which I do).

Surely not all of them have such a strong faith in God that they can pray and go without being able to see :)