It's not that they can't, because they absolutely can - it's that they'd much prefer not to because doing so involves anywhere between locking down ALL aspects of reading memory and adjustments, implementation of kernel level anticheat / rootkits for a fast solution and performance problems due to those restrictions (and potentially more).

That and the potential loss of players that aren't using it to cheat getting punished and essentially being a damage to PR and possibly sub counts.

There is also the occasional set of players that got banned but ended up being pioneers for certain implementation of features we didn't have before like buff timers on Party List, damage types in float text or saveable sets of Waymarks (at the cost of moving waymarks mid fight however) - features that were often told as "impossible to implement, we can't" - yet here we are.

It is against TOS and punishment will be dished out accordingly when confirmed, but a blanket ban is not realistic due to many moving factors.