why-it-is-not-recommended-to-name-a-user-defined-store-procedures-with "sp_"

They are system defined and mostly resides under the master db.
So if we write a user defined stored procedure with  "sp_" the query engine first search the sp inside the master db.
If it is not found it will search the current session db.
This brings unnecessary round trips.
Better to use some other naming conventions like "usp_"

Thanks.