Some requirements are different...
Last week I was at a requirement engineering course.One thing that stuck was, the Kano model, which can be used to classify requirements:

Depending on their category (excitement-, performance- or basic-attibutes) the corresponding requirements have a very different influence on customer-satisfaction.
Basic attributes can easily be overlooked, if you are not familiar with the domain, because often they are not explicitly mentioned.
Excitement attributes are the factor that make the difference.
Over time, with each new product-version, given attributes drift from excitement to performance to basic.