>>31980816Trainers go through puberty at the same time as they develop deep emotional bonds with their team. They spend a lot of time alone, with no one else around, in the middle of the wilds. They often travel with no companions and their parents and older relatives are left far behind, so there's no one to tell them what's socially acceptable or not.
And like
>>31980897 said, the pet comparison isn't exactly correct. Pokemon have human levels of intelligence and emotional development. We see from the games and anime that Pokemon are often extremely close to their Trainers on a physical level, with constant petting and cuddling going on. It's not rare to see Ash and others sleeping with their Pokemon in yhe same bed, Pokeballs be damned.
And even without the human minds, some have pretty attractive bodies by human standards. Humanoids, alternatively buff and muscled or feminine and petite.
So imagine puberty hits you hard while you're surrounded by your best friends, who you trust with your life and who all love you unconditionally, in the middle of nowhere, with no one to watch you or tell you what's socially acceptable. They're always hugging you close and giving you emotional support.
Yeah, it's probably super common.