> Please help me understand this obsession about building a secure software.

You probably already know this, but it's so your things don't get stolen and your computer doesn't get exploited and possibly used against other people's computers. Wouldn't you agree that these are bad things?

> most of stuff on your computer is crap

And the 1% (such as your bank information) is the most important and would affect you the most if exploited, wouldn't you say?

> for an average user the convenience trumps everything.

You're completely right, which is why Flash wasn't disabled until things got really bad.

> All of this is fine if there is a perfect replacement for flash. No, there isn't.

This is also a valid point that could be argued for.