The reason is, that JS is enabled by default, nothing else.
If users had the possibility to actively decide before any remote code will execute on their computer, how many would like to enable it?
We are just one default checkbox setting away from what you call "utopia" here - a word that should be used for much bigger things.
Of utopic naivity in deed is the expectation that such powerful features will not be misused - delivering browsers with code execution enabled by default will be looked at as one of the most funny things of the first internet in a few decades.
Web application development paradigms that enforce JavaScript usage as an absolute necessity are examples of "naive utopian deadends". It is totally anti-avantgarde and anti-progressive, we should not waste so many young talents on that.