Singlespeed chain tension

There's one question that has been puzzling me for a while:

I ride fixed and like every other rider out there I need to re-tension my chain from time to time. Living in the Netherlands this often leads to comments from people witnessing this, such as "is your bike broken again?"
Now it is very easy to explain the need for chain tensioning to a person with derailleur gears, but I never fully figured out what to say to these people with their Dutch-style singlespeed bikes who have never even taken a look at their chain (mostly hidden under a chain guard anyway)?

Why do they never tension their chain, while I have to do it regularly?
Three possible explanations:

• Riding fixed puts much more strain on the chain than singlespeed, so that it wears out more quickly
  
• You need a tighter chain when you ride fixed, because it might slide off otherwise when resisting, skidding and stuff...
  
• Everyone should tighten the chain, some people just care more than others...
  
  

I know it's probably a combination of these three reasons, but what would you say is the main one?
Just curious, thanks already guys!

Pft, just tell them to fuck off.

they don't need to have it tight as they're not likely to spin madly downhill, they'll just coast. they've probably not got track ends either.

a) Maybe because you are a Dutchie, the worlds tallest race, you are mega strong with massive thighs, and stretch chains mere mortals, like us Brits would not ?

b) There are no Hills in Dutchieland, hence you can be well slack

c) your bikes get stolen so often that you never have one long enough

I am curious

• Riding a tighter chain puts much more strain on the chain than singlespeed, so that it wears out more quickly
  

• You need a good chainline when you ride fixed, because it might slide off otherwise when resisting, skidding and stuff...

• Some people should loosen the chain.

Fixed.

With a chain fully enclosed in a chain guard, it's easy to forget it and too much hassle to actually adjust. Also, a fully enclosed chain stays much cleaner and doesn't wear as much.