I was thinking about this the other day in the Context of Magic the Gathering. I wondered if Game Freak ever hesitated to design more fish pokemon for flavor reasons. The earliest Magic sets had lots of Merfolk in them but later on for a period of years they stopped printing Merfolk because they were concerned that it dodn't make sense for them to participate in combat with other creatures. But more recently they started printing them again, but newer Merfolk tend to have legs or some kind of flippers that would allow movement on land. They act like somebody actually gives a shit.