Assuming this is from XIVcensus: "Active players" doesn't refer to players actively playing the job. It refers to players who:
a) Got the Wind-Up minion from the 3.3 MSQ
b) Unlocked the job
There's no mention of a level restriction, so just unlocking the job/class is enough to show up in the statistic. Hence why Lancer numbers are inflated - Many pick that up solely for the cross-class skills.
(Just for clarification here)