My roommates and I were rewatching A New Hope a few years ago, and when Vader says “I sense something, a presence I haven’t felt since…”, someone asked why he just walked off.
Of course, the immediate response was “he sensed sand and ran away!”, but it was a good question. If he suddenly sensed Obi-Wan and this was the only ship that had shown up in the past five minutes, why didn’t he just tear the whole ship apart?
I finally realized the answer:
He wanted to be dramatic.
Darth Vader had dreamed, for years, of meeting Obi-Wan Kenobi again. He had envisioned their meeting, their duel, their final battle, the rematch of the millennium…and he would bury himself in a giant sandbox before he allowed that meeting to open with him lifting the floor panel off a freighter.
So he stormed out, eagerly told Tarkin about this to help him maintain some level of patience, counted for ten minutes (the minimum amount of time it would take Obi-Wan to disable the tractor beam), and then walked into the hallway outside the ship and turned on his lightsaber.
When Obi-Wan appeared at the end of the corridor, it was everything Vader had ever dreamed.