SQL Server by design grabs as much RAM as it can, as aggressively and preemptively as it can, because it assumes it's the most important process running on the machine. Which is almost always the case in production environments, and a reasonable default behaviour as a result. If that's not the case, you can easily set resource limits at the application, container, and/or VM level.

(This comment coming from someone who used to have to support running small backup MSSQL instances on Windows 8 tablets.)