Are design furniture have to be confortable ?  

Paulin's Orange Slice Chair
I was really surprised to discover the versatility and comfort of this chair for various body shapes. It seats my large neighbor quite nicely, his daughter enjoys sitting cross-legged in it, and my girlfriend lounges sidewise. Although I primarily sit in my Eames lounge, I am quite happy in this chair, as well.

Form without function
is pointless in my view. Why own furniture, or for that matter any object, that you cannot enjoy the use of?

I Agree With Olive
Furniture without comfort is merely sculpture.
Although, I can see how a bench might be designed with minimal comfort in order to keep one alert, say, in a church.

So pretentious
Oh gosh, this is so pretentious. Nothing better to do?

I think designer furniture should be comfortable because we buy them for this purpose only. Otherwise, you will have to replace the furniture that not giving you any benefits.