When do all these magic 4kV spikes occur?
If they were at all common,we would have equipment being zapped everyday,all around the world.
In fact we do not,& the Power supply Companies take good care that we don't,with protective devices of various types.
Many of these very high voltage ratings are to provide a very large amount of "headroom" over & above the operating voltages of the system.
In the real world,a decent Tektronix X10 probe can be used to look at the 240v Live conductor,provided you don't connect the Grounding clip to anything & rely upon the 'scope Earthing via its own power cord to provide the return path.
And guess what? You can pre-attach the probe & then turn on the power---then,if I & the tens of thousands of other people who have used this method are wrong,all you will do is blow up your probe,or possibly your 'scope.
You will not be touching anything,so will be safe.
No you would not the high voltage transients are either filtered or suppressed by the inputs of your appliances. Scope probes do not have such suppression because it would corrupt the test signal. They do have input protection but that just tries to clamp the signal at their theoretical maximums.
+1. For Darwinism.
Mains supplies have been around for many years.
Only comparatively recently have devices had such protection,& even now,not every piece of equipment has protection---legacy stuff,kitchen appliances,etc.
Huge voltage spikes on the Mains supplies are incredibly rare,& even in the unlikely event of them occurring,most are of such short duration,as to (1) have very little energy, (2)be substantially attenuated by the inline inductance & resistance of the distribution system.
We have to synchronise you looking at the Mains with your 'scope,& the very rare occurrence of a spike capable of damaging your probe.
It's like winning the Lotto every day for 20 years!
For some reason,some people like to think our occupation is incredibly dangerous.
There
are dangers,but a little forethought can allow you to work safely for a whole career.
Running around squawking like Chicken Little,on the other hand,is pretty much counter-productive.