People have hypothesised the following team buffs:
- Team Instinct (yellow) - Higher CP pokemon from eggs/better eggs (eg. 10km instead of 2km)
- Team Mystic (blue) - Higher CP from evolution
- Team Valor (red) - Higher CP from power up
These team buffs have not yet been proven.
It is just lore/story on a screen at the moment.
Even if low CP pokemon did have something to do with team buffs it would still not matter seeing as there is no "team buff" for finding higher CP pokemon. As mentioned per story/lore per team.
I noticed if I stay around my house I get low level pokemon but after walking around for a bit (walk 2km towards another area) I find higher level CP pokemon and even different types.
Note: When I get back from my walk, most of the pidgeys, ratatas and weedles around my house have higher CP. This happens alot (of course excluding the occasional low level CP of 21 or so which is 1/10 encounters) and they are usually CP 150+
Also note that I am level 14 nearly level 15.