I was wondering the same thing recently about all characters, not just drones.
Pedestrians are threshold 2, and you need at least one net hit to notice something, so in practice you need 3 hits. Of course, you don't need to roll at all if a guy is just standing there in front of you. But if you're driving on a busy street, and maybe even getting shot at, you could easily overlook a jaywalker. Heck, sometimes I forget to look both ways before turning, and only notice a pedestrian at the last moment.
Anyway, it seems to me that if the pedestrian is trying to hide from you, the Perception threshold should be at least 2! But I'm not sure how to reconcile that with the Infiltration rules. Same issue you're having with drones, really.
I was also wondering how to handle ties for Infiltration vs Perception. Normally the "defender" wins ties, and my intuition tells me that's the perceiver. However, the rules do explicitly say that you need a net hit to notice something. Also, if Perception wins, that means you need at least 3 hits on Infiltration just to hide as well as a pedestrian on a busy street. That seems ludicrous to me. Therefore, I'm thinking that I shouldn't break ties, but make them a stalemate: The guard doesn't see you, but only if you stop what you're doing immediately. You stay hidden, but you don't win either.
(By the way, while investigating this, I noticed that the rules use "net hits" a bit inconsistently. It's especially bad in the spell rules, where they define a threshold as a number of net hits. That's a self-contradiction, since net hits are defined as hits in excess of a threshold! Similarly, the spell rules often seem to use "net hits" when they really mean "hits." My best guess is that they're using a threshold of 0 for the simple success tests, much like an opposed test versus an unaware/willing defender.)