Brass tacks, the Steelers don't exactly have a history of keeping three receivers. Even in this era of passing football, the Steelers will pay one receiver while developing a young one on the cheap. When their third receiver comes up for an extension, he's either allowed to sign elsewhere, or he's moved into the Paid Receiver role.
Jerricho Cotchery is, by all accounts, a fine guy and a benefit in the locker room. He played well last season, and age doesn't appear to be an issue. The Carolina Panthers got themselves a good football player on a 2-year, $5 million deal. But the fact the Steelers let him walk is a combination of fiscal responsibility and not allowing themselves to go down the "sign the veteran player" path any longer.
Not to bring it up, but let's apply Warren Sapp's "Old and Slow" mantra to the team. In the past few years, maybe they allow themselves to be convinced Cotchery is the exception to the unofficial Wide Receiver Rule. They sign him for two years, total value of $5 million, put $2 million on this year's cap. Now, they're either going to bank on what they already have in the passing game - the owner of the best 16-game receiving year in team history, a healthy tight end and a pass-catching running back along with the developing skills of a second-year guy (who happens to share many of the same attributes as their best receiver at this point in his career) - or they're going to replace Cotchery with another veteran receiver at a considerably smaller price and bank on their top-shelf quarterback working under the only real team addition this offseason that matters on offense - offensive line coach Mike Munchak and a zone-running scheme to which the line and the running back are perfectly suited - in order to create offensive production.
It's a cost-effective scheme because this team is a lot longer now, and the strength is in the overall value on its offensive line. It has an outstanding quarterback who can lean on one outstanding receiver while forcing teams to remember other receivers are there. It has a good pass-catching tight end who will be fully healthy, and a second-year running back who is a virtual lock for 1,500 yards from scrimmage (probably more).
We wish Cotchery the best, but the Steelers didn't lose 10 touchdown passes in his departure. They freed up 10 touchdown passes from Ben Roethlisberger to go to a multitude of different receivers.