probably because it Depends, If you dont know its safer not to.
long answer (keep in mind i live in canada, im not a professional, this is just what i learned and trust, keep in mind above)
- As long as no wire/bar exceeds its max Amp your safe no matter how many things are plugged in or how long of a daisy chain, the max amp is usually listed.
- all devices should list the max amp they use, add up the amp's of all the devices connected to that wire and if its below your safe.
- if your breaker is 15 amp, virtually all normal extensions/power bars are rated for at least 15 amps which means doesnt matter what you do the breaker should* flip before any damage is done
- if breaker is above 15 amp most surge protectors have protection that will trigger if they exceed their max, most basic "splitters" and extension cords dont, eg if they dont have a switch or reset button they are pretty much guaranteed to not have this protection, be extra carful how much you load on those.
some good rules of thumb to keep in mind, look for imprints or labels that list amps, smaller wires can handle less, damaged wires can handle less then they did before and shouldn't be used, if a wire or connector warms when its in use its overloaded reduce the load on it, especially if it warms quickly.
here is a video that i liked that talks about it as well
https://www.youtube.com/watch?v=K_q-xnYRugQ