If that's so, then why is Pokemon Go incompatible with so many low end Android devices, considering that most teenagers don't have expensive smartphones because they don't have a salary to afford buying them?
Pokemon Go may use more storage space,CPU, RAM, and video chip processing power, so it may not run well on slower Android smartphones and tablets. Nintendo probably rather have gamers have a good gaming experience with fewer crashes and freezes by requiring the phone specs requirements to be higher instead of a lot of users who have bad experiences because their phone is too slow.
Users will complain if a game runs slowly, and crashes, so making Pokemon Go only available for fast and medium-fast smartphones will reduce the numbers of poor user reviews which can make a mobile game fail to be popular, and become profitable for Game makers.
Gamers with slower phones may not be as profitable or very active gamers for Nintendo because they are less likely to play Pokemon Go as often, and buy in-app purchases because of their phone's poor performance, short battery life, and low storage space. People who buy slow phones are less likely to be huge mobile gamers like a user who own an iPhone, or Samsung Galaxy S7 which may play games for longer amount of times, and spend more money on DLC and in-app purchases.
Teens who are 13 or older these days can make money from after school and weekend jobs. Teens can now make money at home online with websites like YouTube, Blogspot, Hubpages, and Swagbucks. There are more teens now who can afford an affordable smartphone with good performance like a $149 Motorola Moto G smartphone which can run Pokemon Go according to a Reddit user at
https://www.reddit.com/r/MotoG/comments/4sg6wp/moto_g4_pokemon_go/ .
I think Teens are not the main audience for Pokemon because most Pokemon fans are in their 20s to early 30s because it was popular in 1996 when teens were not born yet, and people in their 20s where still babies. Nintendo is probably more concerned about getting good user reviews from the biggest group of Pokemon fans who are now in their late 20s and early 30s who own faster smartphones in most cases.