Cost is another reason.

In our environment, when our databases were on our own servers there was no reason not to have a different database for every application and there were 80 or 90.

Then, the servers were moved offsite to be managed by a 3rd party. They charged by the database.

When mandates to reduce costs started coming down, a logical solution was to reorganize our apps into a handful of databases and seperate them logically by schema.

It would, of course, be much more useful at times to be able to switch the hierarchy of how object types (tables, views, stored procs, etc) and schemas are displayed in the tree (so all the objects that belong to a given schema fall together)