Then, you could actually do mixing in apps like DJay straight on your iPad, on a whim, sometimes—without having planned for it in advance—and make it straight through to mastering and uploading the result... unless you filled up your whole iPad with random videos/apps/etc. in the meantime, in which case the lossless versions would be gone, you'd have to work with the lossy copies, and then, when you get home, restore the lossless copies (or transfer the project to your PC) to master the encoding.
So, not so much when you want the lossless version as canonical (most times when you have a lot of space), but rather when you want the lossy version to be canonical, and the lossless version to be there as a sort of "optional file to enable mastering using this track" file, that's sometimes available and sometimes not.
I have about 600GiB FLAC music from bandcamp, random publishers, and CDs. I then have, separately, the same directory structure but encoded as 96k and 128k Opus. Still all fits just fine on a mere TiB disk. In a couple years the difference between 96k and 128 in terms of space won't matter and I'll drop 96.
And yeah, it's very nice to have the FLACs when I want to timewarp, transcribe, analyze, or remix. I usually do that at home though, so I can splurge on the bandwidth.
WRT the Internet Archive, Wavpack hybrid decoding is probably too slow and too rare to bother including in any major browser. Even if they did, if lossy listening is a priority, a dedicated lossy codec will save them money in short order on bandwidth. Indeed, this is exactly how IA does things, they even have wav in addition to flac and two or three lossy versions of (almost?) every recording.