But why would they change the convenience of shopping in the app?
Because Apple wanted to start charging 30 percent commission for every sale made that way (if the app sent you to the store directly).
No doubt that is part of their thinking. Though since they added an out it was not something they were going to force. What they said publicly was that they wanted to make sure that in-app purchases were consistent in order to avoid confusing customers and ensuring a quality experience.
And before we get too self righteous about the whole thing there are two issues to take into consideration.
The original rule, that did not allow the simple removal of the link, was pointed at subscriptions. Book readers just got caught up in the sweepings.
Second is that Apple is providing an extremely valuable retail venue for these companies, and by their current rules those companies are paying all of $99 a year for that resource. That has to hurt any business man's greedy heart.
And it's not the norm for other companies, so jumping on Apple for it is pretty close to the (typical) only blame Apple bias that permeates some news sources, and a multitude of blogs.
For instance, Amazon offers newspaper and magazine subscriptions. Do they offer 'any' way for those periodicals to avoid paying a percentage to Amazon? No, they don't.
To be fair, Amazon's business structure would make it inconvenient to do this. And it would be pretty stupid of them since this is how they make money; selling things.
And to be somewhat more critical of Apple, it's business structure means that even when they do not offer direct profit, companies like Amazon add value to the iPad platform that is sure to result in indirect profit.
It's all pretty complicated, and motives are slippery things to assign. I'm just relieved that it did not come down to an industry wide battle that resulted in a loss for everyone.