If you don't route the feed line away from a center-fed dipole antenna at 90 degrees, it will be in an unbalanced RF field, and thus will couple to the unbalanced RF field, to some degree, even with a perfect (infinite impedance) balun.
Depending on the distance and angle of feed, an RF coupled feed line can act like an angled antenna director or reflector element and distort the antenna pattern, perhaps sending it off at some undesired angle. (or perhaps, if you are really lucky, or design for this pattern, adds gain to your desired direction).
A bazooka balun will reduce direct electrical coupling, but the high voltage RF field near the dipole tip will still couple to the feedline shield at some distance away from the balun. You can simulate this by putting an unconnected wire next the nearby feed line, using something like the NEC antenna modeling software. At certain distances and lengths, a completely disconnected coax shield will pick up plenty of RF voltage if not closer to 90 degrees from dipole center.