Happened to me early in my driving career with a motorbike, I could not see it and not hear it, then I attempted a manoeuvre and had a very angry motorcyclist appear from out of my blindspot. I could have easily hit him.
This is what made me eliminate my blindspot through moving around in my seat, looking over my shoulder, correctly adjusting my mirrors and constantly monitoring and focusing on my driving (never have loud music on ever since).
Have also had two close family friends killed by motorbike accidents, so I am extremely conscious of the vulnerability of other road users.
Exactly. This is solved by hyper-vigilance, nothing else. In 30 years since I can honestly say I have never had a case of not seeing someone / being surprised.
You can eliminate your blindspots completely, but it takes a specific mindset and anything that gives you a false picture (eg I glanced at my mirrors / used a signal) is a barrier to that mindset.
Indicating isn't a solution, it is part of the problem. I had learned to always indicate, and it had given me a false sense of security that indicating made it ok if I had not seen someone. The complacency of feeling safe if you always stick on a signal was what was wrong with my driving.
So, now I am aware of everything around me and when I signal I have certainty that I know precisely who I am indicating for.
You have this completely and utterly wrong.
It may surprise you to hear I agree with a lot of what you say, and commend you on your heightened awareness and vigilance when driving, but unfortunately by your own admission this came about by a close call (that could have had much more serious consequences) and sadly some close personnel experiences.
The reality today is a very high % of drivers on the road do not possess all of your exceptional combination of skills ( training, experience, hyper-vigilance AND patience) and because of that they will make mistakes,
I'm sorry, but you saying that people always indicating is part of the problem is just arrogance on your part
Looking back thru this thread shows there is definitely divided opinions on this,
Nearly every time I (or you) go out on the roads we will see examples of distracted, careless and sometimes plain dangerous driving, do u think many of them people share your driving prowess/concentration levels?
I've never implied that indicating is an alternative to proper vigilance,
Human nature is that a lot of people aren't always going to be hyper vigilant and as a (albeit much inferior) alternative I'd prefer they at least indicated their intentions
Remember rules are for the masses not the elites, and "perfection is the enemy of the good"
As also pointed out earlier by
@Ian Key
I was taught to always indicate for my car test, only to indicate if someone benefited for my IAM test and back to always indicating for my PCV test. All of which I passed first time
To borrow a medical saying "doctors differ, and patients die"
Even driving experts disagree on the whys and wherefores on this topic
You have this completely and utterly wrong.
Hope the view is nice from your ivory tower,
I prefer the more polite - we'll have to agree to disagree on this
Lastly consider if everyone drove perfectly they'd never be a crash - and for that matter seatbelts and airbags would be redundant, but welcome to the real world!
) who told me decades ago that a good driver doesn’t need to indicate at a roundabout because it’ll be perfectly obvious where he’s going 
lol
