It needs to because otherwise supply voltage drops and you get brownouts. There is no provision in light switches, outlets, thermostats, industrial machinery,

It needs to because otherwise supply voltage drops and you get brownouts. There is no provision in light switches, outlets, thermostats, industrial machinery, or anything else to first check "is there enough current in the grid right now to run this?". They just draw current when connected, and changing that policy would be a huge endeavor.