What determines how many Poké Miles you earn from Streetpasses, and is it possible to increase it?
I ask because I always only earn a single Poké Mile per hit, which seems hilariously low considering any kind of online interaction yields far, far higher numbers – I think a single Wonder Trade yields about 40. It's not even worth bothering checking the Streetpass data for: I have ~13,000 Poké Miles in total, of which only about 10 were gained through Streetpass. Granted, I Wonder Trade a lot, but that's still a ridiculous ratio.
Best Answer
Pokemiles are calculated by the distance between your home location and the other player's home location. So by Streetpass, you're mostly getting people from...basically 0 miles away.
Streetpass is generally pretty useless for Pokemon XY for this reason, and I would personally suggest ignoring it. If you want more, you could make sure to walk/drive past Streetpass relays, but your time would be much better spent simply wondertrading a few pokemon to get the Pokemiles. Since a good percentage of wondertrades are from Japan and the US, which are of course a good distance away, wondertrading will very often yield a fair number of miles.