Well, objectively, you can't call something wholly unnecessary when there are many thousands of of groups to get through.
The search function is fine if you are on rails and know what you want to find. But strolling through the landscape to see what unanticipated wonder you stumble across also has merit.
An important point is that you can choose not to use it and include all categories in your sort or search. So you lose nothing while others gain something. It limits nothing and adds flexibility.
It's about the greatest choice for the greatest number. You can still do things your way. Those that want to can do it another way.