Why the runtime libraries are installed side-by-side is explained in the German blog post Windows 7/8.1/10: Fehler Side-by-Side-Konfiguration ungültig, but in an other context.
If VC++Runtime libraries are updated by security updates, Windows installs them in most cases side-by-side. With Visual C++ this is the redistributables (runtime libraries) that are installed with the respective application.
Most programs require runtime libraries to run.
