In most contexts, "IPFS" really just means "self-hosted", because it only works if someone who actually cares about the file (in practice, just the author typic

In most contexts, "IPFS" really just means "self-hosted", because it only works if someone who actually cares about the file (in practice, just the author typically) is seeding it. For Sia/Skynet, the Sia network is doing the hosting, meaning the file has high uptime even if the uploader does not, and even if nobody else chooses to pin/seed the file.