"Why?"

Because it's obligatory. I said so, didn't I?

As to merits, agreed that it's a different mix. Avoiding lock-in is itself a good thing for the customer. You don't need to hire a sack of people to benefit from it either. You could hire a specialised consultancy in the odd cases you need to add some feature to an existing program. Sure it costs a lot, comparatively (oh noes! ten grand to fix a free program!) but that's not how to calculate. The trick is to find a shop or a freelancer with good ties to the community, so the changes get mainlined (eventually, maybe you might want exlusivety for a while) to help the feature stay alive. Such a shop stands on "free" shoulders, so you only pay for that work, not for everything that's gone before. Since you're not paying for it, it tends to be overlooked. But it's easily thousands of man-hours you get for free. No licences, no yearly fees unless you intend to retain these people. And if they fsck up, well, you find a different consultancy, maybe even take the partial work to the new bunch to fix. I've worked for such a shop. We even got work from another foss-focused shop who could just as well have done the work in-house, in theory. It might take a while to wrap your head around it, but it does make sense.

FOSS generally has a much higher scratch-an-itch vs. tickbox item ratio. It doesn't need to be sold, so the revenue doesn't have to prop up a force of cheesy salesmen. It doesn't need to show off eye candy, which is presumably what you're mistaking for user interfaces. Open source has less of a tendency to bite many years down the road when you need to recover archives for this or that reason. If corporations don't value any of that, that's their outlook. Most corporations don't have much in the way of great people, and most don't last, either.

You're right that open standards are at least as important as open source; both for avoiding different kinds of lock-in. Your examples of "open formats" are rather poor, though.

"more effort put into user interface design"

Abominations like the ribbon, and putting touch interfaces on the desktop? The less UI design the better.