tzefp8ezfn7h, the devs dont provide index.html/php files for whatever reason. They are aware of the result. It's only been recently that they even included one inside wp-content/
Why doesn't WP come installed with directory listings disabled?
See above. And realize too that the devs are never going to go for editing .htaccess files beyond what might be done for pretty permalinks. In other words, they don't believe, and neither do I, actually, that they/WordPress ought to be editing your .htaccess ...
Thats your job.
The lack of index files has been a sore spot for a lot of people.
But thats not nearly as bad as the path info that can be gleamed off some of the files.