Most of the product management literature focus on building products customers would love. But in reality, and especially in the B2B market, it is more important that customers are able to buy your product than them loving your product. For example, it doesn't matter how crazy some CEO is for an iPhone, unless her company's internal policy allows it, she won't be able to buy one despite all her power. Another good example I know is selling custom software to enterprises where quality of engineering solution and end-user satisfaction are very low on the list of factors influencing success of a product.
In the world of enterprises the impulse buy is almost non-existent and every purchase decision of non-negligible amount must go through several steps in order to be approved. If you're selling a standard product than the procedure for buying such product has already been established and the role of your salespeople is to demonstrate advantages of your product compared to offerings of your direct competition. But if you're trying to introduce something new to the market, you face an uphill battle since you have to prove not only the merits of your solution, but also help your customers buy it. Establishing the right procurement process for a new type of product is very complicated and time consuming, and it requires in-depth understanding of customer's organization and politics. First, you must identify the right person who has authority to make a decision and find a way to get his or her attention. Second, you must convince him or her that choosing your product will somehow boost his or her influence and standing in the organization. Third, you must identify all stakeholders who can block or stall the purchase decision and either address their concerns or make sure that the purchase decision flies under their radar. Fourth, you must make sure that the decision maker has a budget available since changes to a budget are close to impossible to make once the money is divided by the power holders. Fifth, you must make sure that buying your product doesn't run against some internal policy which is again something close to impossible to change. Sixth, once the letter of intent is signed you must make sure that legal concerns don't derail final purchase agreement. Finally, you must make sure that implementation of your solution doesn't wreak havoc to organization or you risk revolt by actual users of your product.
It is evident from the long list of issues I've described above that selling to enterprises is different and it requires a very specialized knowledge. That's why good enterprise sales people are worth their weight in gold.