I get that the gist of this thread is "WP bad", but to be fair I've ran relatively often into the opposite issue in ProcessWire: an image or file that should've been uploaded once and then reused is instead uploaded to a whole bunch of separate pages, using loads of unnecessary disk space. ProcessWire doesn't by itself create a lot of unnecessary variations, but it is not uncommon occurrence either: years of code changes combined with badly configured image fields (no limit for image dimensions) can lead to major disk bloat.
Worse yet is when someone decides that a file/image that is separately uploaded all around the place now needs to be updated everywhere. Oh the joy!
Long story short: there are cases for and against both central media/asset management and page based media/asset management, neither are perfect.
Now what is indeed suboptimal is the way WordPress handles variations: they need to be globally registered, are created on upload (whether you need them or not), and won't be (re)created automatically if registered or changed later. This can absolutely lead to unnecessary disk usage, and on the other hand means that you may not have the variation you were looking for available, or it may not be what you expected it to be. But again, each approach/architecture has upsides and downsides ?
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By the way, I'm not generally against bashing [insert a CMS or any other product here] or venting frustrations about it, but I do think we should try to be fair. WP gets a lot of bad rep for a good reason, there are definitely issues and shortcomings, but it also gets blamed for legacy/aging custom (site/theme specific) code, overuse of third party plugins, outdated third party plugins, etc. None of these are core issues, and it's not really fair to blame them on WP ?