So many clubs with really shitty power or who haven't bothered to figure out how the power needs to work. It used to be smaller clubs or bars when it used to be things like the beer fridge would be on the same circuit or maybe the window neons, etc. Later it was bigger rooms but we'd find the 'production' (lights, smoke machines, etc) would be tied into the same circuit...that shit is hard to suss because you're not using it during check, but come showtime, all that is running and what was clean and perfect for check gets ugly fast.
My thing for stage setup was to have unlimited clean headroom (all tube high voltage pre's, super big power stages)...so my most current touring rig uses an amp that was built for me using Hypex units... it's 2500w RMS and peak is closer to 3500w or more. So, yeah, that circuit is really important. Also, if power gets clustery, the IEM setup and the wifi that controls it for the monitor mixes gets super erratic and futzy.
*I also prided myself on a non-pushy hospitality rider. The thing that got the most pushback was 10 9v batteries, which was the least presumptuous inclusion...Batteries for the stage wireless units. Once people understood that, they stopped questioning it.