Looks like we disagree on what's a bug and what's a feature in a file picker. But the mirrors on a car are mandated by law, so the equivalent for that would be a missing Cancel button (which forces you to always open a file). If I had to pick a car part equivalent to the file thumbnails, it would probably be seat heating or a built-in navigation system - it's nice to have (for some, others never use it), but you can use the car without problems if it's broken or not installed.

I'm not saying that it's not a nice feature to have, but it's also definitely non-trivial - it's not only thumbnails for images, if you do that people will also demand thumbnails for videos (including, of course, all ancient formats), PDF files, Word/Excel/PowerPoint documents, HTML pages etc. etc. etc.