Why use www?
This reasoning is all based on valid, but technical issues for the hosting side.
A general rule for any customer-facing business is to put the customer first. I could list 200 different reasons why you should make the customer register an account with their email address before they can purchase something for you. However, if you put the customer first, in many cases it is easier for them if they don't have to do that. Having the www before the domain name adds unnecessary visual clutter and from the customers point of view, an unnecessary redirect before they can get to your site. A lot of sites use minimalist style everywhere, and it's great. Having the www there for technical reasons is putting the user second in those cases.