One of many reasons why using the plain * operator in JOINs is ill advised :

One good principle to adopt early on is this to select what you need, and need what you select. What I’m
getting at here is that every additional record or column that you return takes up additional network
bandwidth, and often, additional query processing on your SQL Server. The upshot is that selecting
unnecessary information hurts performance not only for the current user, but also for every other user
of the system and for users of the network on which the SQL Server resides.
Select only the columns that you are going to be using and make your WHERE clause as restrictive as
possible.