The old reason for shared libraries was to share memory/cache and not waste disk space. That's not gone, but maybe it's less important than it used to be. The

The old reason for shared libraries was to share memory/cache and not waste disk space. That's not gone, but maybe it's less important than it used to be. The modern reason is maintenance. If 100 apps are using libfoo, in practice nobody is going to maintain a hundred separate versions of libfoo. That means your choices are a) have hundreds of broken versions nobody is maintaining spread all over, or b) maintain a small number of major releases forked at the point where compatibility breaks, so that every version of 1.x.x is compatible with the latest version of 1.x.x and every version of 2.x.x is compatible with the latest version of 2.x.x, and somebody is maintaining a recent version of each series, so you can include it as a shared library that everything else links against. But then you need libraries to limit compatibility-breaking changes to once or twice a decade.