Thats because those are the best maps. We had an awesome game on EJOD the other day, MEC forced back to its HQ but then regaining a flag, vicious
Its showing as 17% because of the 16p being the starter map too
Im all for variety, if it were down to me I'd have every map ever made for PR or even a couple stock maps (jalalabad, wake island

), on the map list.
That'd probably lead to more crashes, its not legal by the devs and some of those old maps would play weird but it'd be fun to have a map appear at least once a fortnight imo.
The devs want just a few quality maps I think, not the old 20 mins a round vanilla style
The maplist has changed lots anyway recently