Reporting Services puts parameter selection before the top of the report, with (at most) 2 parameters on a row. If your report has a lot of parameters (my example below has 5), the parameter section can take up a lot of room:
As an aside, having multiple parameters is better than having multiple reports which differ only by a WHERE clause in the database. Parameters are your friend - it's just the parameter display (which is not configurable at all) that I'm trying to look at here.
So taking up a lot of screen real estate with parameters is a bad thing....