Torrent hosts do not have a monetary incentive to host files.
Filecoin (and other decentralized storage systems) provide monetary rewards and penalties for storing or failing to store files. This is introduced in Section 4.1.1 of this paper.
Exactly. As long as there's demand to keep hosting files in the network, there WILL be providers hosting your files. Even if a hosting company who hosts 5% of the network (that's a lot) decides to exit the and stop hosting, your files are spread between enough computers and you only need about half of them to be online to recover your files.
Unless some parts of your data happened to be replicated across multiple shards on that same hosting company's hardware. Then you would have a partial loss of data.
The bad thing is that you would not be able to hold them responsible.
I think it's a problem of reputation, actually. Google and Apple keep stuff online because they promised they would, and there would be backlash if they turned it off all of a sudden. There's nothing stopping a random, anonymous "filer" (like miner) from stopping the upload stream.
To go even further, if you orchestrate several miners carefully (maybe computationally) they can together perhaps stop people from accessing certain files.
Filecoin (and other decentralized storage systems) provide monetary rewards and penalties for storing or failing to store files. This is introduced in Section 4.1.1 of this paper.