Well I bought Mobil 1 when it was on sale and I get the dealer to put it in. The price comes to the same as if I had used their dino oil because of their typical stealership markup.
As for why I even bother, well I like the piece of mind of having an oil thats supposed to last better under harsher conditions.
And saying that your previous engines worked great with reg oil and reg oil changes although true can be compared to a lifelong smoker who never gets cancer. Yes it might work for you but doesnt mean that not using synth or quitting smoking is the right way to go.