Zz.
The lack of ranked AR10 maps is mostly due to the fact that they don't have a difficulty spread to go with, rendering them unrankable.
Also, in the past, people heavily misused AR and put AR9 on maps that desperately need AR10, an example being ztrot's and BD's Renard Pony map, or Atama no Taisou. Freedom Dive would go well with AR9.5 btw, but we didn't have that option back in those times.
Even today AR10 has a bad reputation and is supposedly "only used as difficulty factor" which is of course utter bullshit. (tbh I'm pretty disappointed by the majority of posts in here, are you guys really still that ignorant?)