>>55879060We have examples of lv 50 or even lv 100 Charmanders in Battle Towers. The anime has also episodes where a tribe of Bulbasaurs/Ivysaurs are lead by a Venusaur and Squirtles/Wartortles are lead by a Blastoise.
Maybe evolutions rarely happen in the wilderness and evolved Pokemon are something like chiefs of their tribe/herd?