Splitters so that you can control what is happening on stage through your own IEM rig and let the venue deal with FOH. Slightly more cables to carry, but how much fun is a gig where you cannot hear what you need and the wedges are too loud/quiet/distorded?
https://www.amazon.co.uk/BEHRINGER-ULTRALINK-MS8000-Microphone-Splitter/dp/B016BIDFI8#customerReviews