A good reason: IPFS is perfect for distributing packages. Without relying on expensive hosting or a network of mirrors maintained by volunteers splitting the cost of bandwidth limits.
Packages are immutable and content-addressing provides additional layer of security.
Distributing them over IPFS would also make it easier for users of free and open software to contribute (by sharing bandwidth as opt-in).
There is an ongoing discussion about using IPFS in ArchLinux, and even better one about NixOS.
In general, any package manager that downloads data over HTTP could use IPFS (via HTTP gateway), but you need someone to set up continuous automation that downloads updates and publishes them to IPFS/IPNS first.