Why do players get cut when draft picks get signed?

I know its been a minute since I've posted an entry here and on FootballOutsiders for that matter. The month of June through mid-July is the league's downtime as folks try to recharge their batteries prior to the opening of training camps and the season. So from a news perspective, it's a slow time in the league (aside from Cassel & Suggs' new deals). Anyway, I just wanted to post something real quick.

I was reading how the Browns recently signed three of their draft picks, and as a result of their signing, the Browns cut three players. In the offseason clubs have an 80-man active roster limit to account for clubs wanting to have as many players as possible to compete for roster spots. When clubs select players in the April draft, not only do they sign a contract tender, but the draft picks go on the "Reserve/Selection List" list. The result is them not counting towards this 80-man roster limit, as they are not considered "Active." However, college players who are not drafted and subsequently sign an undrafted rookie free agent contract with a club count as Active and therefore count against the 80-man limit.

So when a drafted player signs his contract, the tender that he signed after the draft goes away and his newly signed contract takes affect; and from a roster count perspective, he moves from Reserve/Selection List to the Active roster. Therefore if a club is at its 80-man limit, a player must be waived from the Active roster in order to make room for the draft pick.

The decision to figure out who to waive is not always a simple decision because clubs like to go into training camp with a certain number of players at a given position to account for saving the legs & reps of veteran players. For example, some clubs like to have 10 wide receivers at the start of camp so as to not burn out the legs of your valuable wide receivers, but having 10 receivers may mean having one less offensive lineman in camp and, to their chagrin, more reps in practice for your veteran offensive linemen.

So signing a draft pick to your Active roster is simple roster management, but you don't want to waive that one player who turns out to be a solid contributor elsewhere thereafter.