It's not really as "important" as it is just something that people want. And most of them for no good reason. Same thing with TV's. I'm into home theatre and I help a lot of people buy and set up their new TV. People will spend more money getting a 50" TV rather then a 46", just because it's bigger. And even though the optimal viewing distance would say a 46 is perfect, they still go for the bigger one, again, just because it's bigger.
I see the same thing with speakers. I'm a Paradigm guy and I always recommend them whenever I can. I always see people looking to spend a ton more money on bigger speakers when smaller ones would sound exactly the same given the room size and dimensions. They will NEVER use the power of the bigger speaker and sonically the smaller ones would sound just as good. But because they are bigger people will waste money thinking their getting something better. Even after listening to both. It's crazy, yes. But it happens all the time with many different products.
Just another quick one...my friend who is a casual computer (Internet, email and maybe a document here and there) was buying a new PC. I tried taking him into an iMac but he wasn't going for it. Anyway, long story short he spent a few hundred dollars extra to get a 1 TB hard drive vs 500 gig and 8 gig of ram vs 4. It was a complete waste. He will not even use 50gig of space and will never run anything that 2 gig of ram wouldn't handle effortlessly. But he just thought it was BETTER to have more space and more ram. Just a total waste IMO, but he had to have it.