IPFS requires "pinning" content for it to exist, meaning you host it, whoever pins content becomes liable for its distribution, if no one pins it, it disappears. That's why you can't freely host things like child porn on IPFS.
Select users who have the decryption key (communicated out-of-band) might be willing to pin the encrypted data for the benefit of others who also have the key. There are also for-pay pinning services who probably wouldn't care whether the data was encrypted. And whether it's pinned it or not, as long as it's downloaded the data remains available to be shared (at least until it's GC'd).