PIDs are great for espresso boilers where you want water around 202F (sea level), so below boiling. My home machine with an 800ml brew boiler stays within +/- 2F all day with the PID. My previous machine without PID could barely keep it in a +/- 5F range.
For steam boilers, pressure stats are actually quite effective, especially as they get larger.
For steam boilers, pressure stats are actually quite effective, especially as they get larger.