it's useful in lots of things. one of them is farming system for example.
if using normal switch...
4 switch for EACH event:
no switch for soil state
1) for seed state
2) for plant state
3) for plant state 2 state
4) for harvestable crop state
means if you have 10 Turnip. you will need 10 * 4 switch = 40 switch.
with self switch. you only need 4 self switch each. and it would easier to event too. since the event CAN be COPIED!!!.
with normal switch it won't be possible since you need to modify the switch OR all your turnip will ALWAYS have the same STATE.
of course farming system is more complicated than that. since you also have different type of crops. so if you use normal switch... it will be HELL to event.
edit: just read racheal post above and want to add some.
if you use self switch for chest. you CAN copy the event easily. and just change the item given if necessary.
if you use normal switch. AFTER you copy it. you must change the switch reference too.
maybe it's like only reducing 1 step. but if you create 1000 chest. then it reduce 1000 steps total.

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