This is because the Maven repository format is simple: it’s a directory convention + an xml file on each directory to indicate dependencies. It’s easy to implem

This is because the Maven repository format is simple: it’s a directory convention + an xml file on each directory to indicate dependencies. It’s easy to implement and host in any web server. Other tools (Ivy, Gradle, SBT) can consume it. But, in essence it’s the same with npm and yarn: both get packages from the npm registry (the common denominator is the repository format).