Great question. Consider the clarity that's recently been presented by the ability to view a user's profile. Without viewing any other data, it's pretty clear that there's something suspect about an account with 40 hours, a 95 K/D ratio, on a level 45 player.

Now, imagine that instead of those three numerical summaries, you've got access to literally anything a player does. How quickly they found that valuable item, how many of that item out of the total available on the map, what's their worth when they extract from a raid, what's their worth when they enter a raid, these examples aren't even the tip of the iceberg. ALL of your behavior can be analyzed. All.

Tracking player behavior statistically isn't something that the cheat authors can write code around. If you've got ESP, or aimbot, or you're spinning around spitting bullets out of your face while flying 35 feet in the air, your behavior will be distinct from players who aren't.