From a C/NET interview with Bose VP Sean Garrett:

Over the years the headphone plug or connector on Bose’s headphones has changed, going from L-shaped to straight. In the headphone world, the conventional wisdom once was that a L-shaped plug was typically more durable. Also, the stubbier L-shaped design took a blow or tug better, putting less stress on a device’s headphone jack.

So why did Bose move to a straight connector?

Garrett: We started with a straight plug, then switched to a 90-degree [L-shaped] plug, thinking that it would provide a more robust and durable solution for customers because it wouldn’t have the lever arm on the jack so you wouldn’t break the phone or the plug.

Turns out we don’t get to dictate the geometry of the connector that goes into the phone. So we’re not making design decisions so the connector will fit in cases better; we’re making design decisions so they’ll meet the specifications that Apple gives us so we can be part of the MFi [Made for iPhone/iPod/iPad] ecosystem just like everybody else.

What we’ve discovered is that when you go to a 90-degree plug they’re getting so small there’s not enough room to make all the electrical connections you need — robustly. And that was always the weak point of our cable; it was always breaking there [at the plug]. We went to a 45-degree plug thinking we’d have more space but instead it’s just aggravating because it spins and is never really lined up and gives a bad customer experience.

We’ve also discovered that most phone manufacturers have jacks at the top and mostly at the bottom of the phones so the straight connector is a much better customer experience when the phone’s in your pocket. You naturally slide your phone into your pocket so the cable comes straight out of your pocket first.

Interesting insight into how Apple design decisions throughout the industry.