Reason why pixel bots dont get detected right now: packet bots are first and foremost FAR more effective and efficient at what they do. not only that, but they are widely more popular. JD and the Ibot developers do their best to mimic the packets and packet rates that a normal player would create (as well as the encryption that they have to decode).
As far as pixel bots go. the BP detection scripts are based on the altering and implanting of new packets into the system compared to normal players. pixel bots dont create, read, or send any packets. so this is pretty much safe. BP will also look at hat you are doing, how efficiently you are doing it, and for how long. so any bot running for 72 hours straight will cause a red flag. as well as doing inhuman actions like clicking very fast. pixel bots are not only very random (if you use a lot of randoms in your code), but also are about as effective as a person playing the game. so the differentiation between a player and a packet bot are very difficult. the only thing left to really look at is play time. which is all under the users control how long they leave it on for.
so the anitban measures needed for a pixel bot are much much less than a packet bot and just by thier nature are hard to detect. this is probably why i have NEVER herd of someone being banned by a pixel bot.