It's way easier to recognize an icon at a glance, rather than scan the filename to locate and read the extension.

And the application icons are often super ugly, and often don't distinguish between the filetypes anyways.

Honestly, I'd rather do away with default application handlers altogether. Every time I double-click on a .jpeg, just ask me if I want to open it in Preview or Photoshop. When it's a .pdf, ask me about Acrobat or Preview. When it's an .mp4, ask me about VLC or QuickTime.

I have different reasons for wanting to use a different app each time (do I want to consume or edit, and edit how?), and trying to remember which one is the default handler and when I need to pick the non-default one is cognitive load I don't want to deal with.

Especially since the application-specific icons also sometimes don't even always make it clear which app it is. E.g. the IINA player assigns its own dedicated icons to video files, but you'd never guess that they open IINA.

Just give me standardized icons that are recognizable at a glance, and let me pick the application I want to use at the moment.