It’s not about the devices. Kobo books are very easy to remove DRM from, and don’t require owning a physical Kobo device or their app to do so. All it requires is two Calibre plugins. Also, I might be wrong, but it seems Kobo has a lot more DRM free books in general, compared to Amazon.

Kindle has always required either the Kindle app or an actual physical Kindle to de-DRM.