"Ive started putting crap pokemon in gyms"

#PokemonGO: I put a CP121 rattata into a gym just now. Is it just me or is there no point to putting high CP pokes in there? You lose the mon until the gyms taken over and you cant use it for raids.Is there a difference to putting a high CP poke in? Whats the motivation to do so?Ps: loving the eggstravaganza!Edit to add: Im in Australia. It's 9:36am Tuesday morning here. PoGo is a worldwide game ☺Edit: Ive spun "hatch an egg" and seen a huge increase in bunneary spans so I thought the event started already. My bad via /r/pokemongo http://bit.ly/2DfuVCN