You don't have to, but unless someone decides to "pin" it it might just disappear at any time. So you better pin it yourself or find someone reliable to pin it for you.
I'm all for IPFS, but I think you're missing the forest for the trees. Crypto is hard, especially PKI. KeybaseFS is crypto first, global FS second, while IPFS just says "do crypto yourself" - which, as we've seen with email and texting and literally everything else, doesn't work.
I would love for KeybaseFS to work via IPFS instead of their own servers. But pointing at IPFS as a /replacement/ for this crypto+FS project is disingenious.
How about something completely decentralized, but permanent:
https://ipfs.io/
https://youtu.be/HUVmypx9HGI
The InterPlanetary File System (IPFS)