1: We're a rushing team first and foremost, and DK Metcalf was one of the best in the draft at blocking downfield. His size and strength creates a mismatch for DBs.
2: We didn't bring him here to run out routes. Wilson is always looking for the deep strike, to the extent of being rather infamous for not seeing/using dump-off passes. He would rather extend the play and go for the home run ball. Metcalf is here for getting in the end zone, plain and simple.
3: There is absolutely nothing wrong with being a one-trick pony until someone can reliably stop that trick. Until then, DBs can choose between review-able pass interference, or long receptions. We have the best deep passer in the league, and as stated before, he's a willing deep passer.
4: We now have two legitimate deep threats and a strong rushing game. The opposing defense has two safeties. It takes true skill from the defensive coordinator to cover three things with two guys.