Non EHU Disasters

When ever EHU v NonEHU is mentioned there is always a very polarised response. 

The majority of our carravaning is done without an EHU now of course if a hook up is available I will use it provided I have remembered to put the lead in the van. 

It seems to me I am in a minority so my question is to all those people who simply MUST have an EHU have you actually got any experience of not using a hook up and what was so disastrous?