Actually, they shouldn’t make applicants sound whiny: “I want, and I want, and I want, and you should” is not how a cover letter should read. The letter should be all about the company’s needs, and very little about the applicant wants or desires—except about how the applicant’s goal is to exceed all of the company’s needs and requirements. The applicant would be better served to say that she has done X, Y, and Z before, and she can do it again.
In short, it’s not about what the company can do for you and how it can support your goals. It is about how you, the applicant, can improve the company in so many ways.