This seems like a no brainer to me and genuinely confused me when I found this limitation.
According to the help documentation "The global search results are based from the Catalog, Manufacturer, and Assembly Code column records."
We use many of the columns outside of just those three. One of them is extremely important to us because it includes our ERP system's numbers. Many employees here know the ERP numbers by heart and not the manufacturer's numbers.
Allowing the global search feature to search all of the columns, or possibly a selection made by the user, would be way more helpful for us.