wbntff then write another extension 'no self likes' which is not updated since 7 months
The difference here is that the bundled Likes extension is maintained by the Flarum team. The No Likes extension was built by a community member. Would they have contributed that change to the Likes extension it might have already have been part of the Likes extension.
Regardless of this, usually we recommend people to use/build extensions for changes they particularly need. It keeps the code easier to maintain for the small team working on the project.