Ive been to a couple of jobs where the customer has told me that they need a rewire, it then turns out that a new CU with a couple of extra bits (sockets, circuit or whatever) are all that's required.
Sometimes, they're over the moon at saving a couple of grand. Sometimes they doubt it can be so because "the other electrician said the wires need replacing because they're old colours". Pointing out that the current install is likely far better quality and standard than 'ripoff & leggit' are going to give them doesn't always sink in either.
I don't loose sleep over it, I'm an electrician not a moron therapist.