Because it’s effort. People will want you to make enhancements and maybe expect changes. It may link to proprietary libraries. Open source is not really just about dumping code on GitHub.
> The only people entitled to say how open source 'ought' to work are people who run projects, and the scope of their entitlement extends only to their own projects.
To be clear, if someone wants to just do a code dump under an open source license, ignore it, and send any communications about the code to /dev/null that’s their choice. Probably not a very useful one but a valid one.
> Open Source is Not About You
> The only people entitled to say how open source 'ought' to work are people who run projects, and the scope of their entitlement extends only to their own projects.
https://news.ycombinator.com/item?id=18538123