I think you will find that the internal tapware and hot water service is not rated over 350KPA. I have tried mine carefully without the regulator and the flow pressure is not much more.
Some towns you go to may have extremely high pressure and some may have above average pressure and you might not realise. Comments have been raised in the past on other forums about just turning the tap that feed the van on less. But, the problem is when all the taps in the van are closed, the pressure still remains the same and you have only really reduced the flow rate.
The pressure reducer is there to stop you blowing your fittings to bits and having the dreaded water leak in you van. All vans generally have them. Things like campers sometimes don't as they do not have HWS's in them. When you add a hot waster, it time to add a regulator.
Can you imagine coming back to your van after being out for a couple of hours to find a pipe has failed!!