Modern computer security is about removing as many known possible attack vectors as possible.
So that's the benefit.
EDIT: to those saying browsers are sandboxed or that there's nothing sensitive, it projects against e.g. Comcast injecting JavaScript into pages from other sites. [1] There are all sorts of types of bad actors out there. Surely I don't need to list them all here.
[1] https://thenextweb.com/insights/2017/12/11/comcast-continues...
A malicious actor hijacking plain HTTP connections does not necessarily have to inject code that harms the user's computer directly. He/she could also just alter bits and pieces of the served content to trick the user into doing something not in his/her interest.
So while having better browser sandboxing and protection is good (and welcome), HTTPS is still necessary.
If so they are only insecure because malicious JS can be MITMed into them, and realistically speaking browsers can’t defend against malicious JS.
> Modern computer security is about removing as many known possible attack vectors as possible.
So let’s remove enabled-by-default JS permissions instead of removing HTTP-content. Most old websites don’t depend on JS and would in fact be just fine.
Even better: make JS opt-in only for HTTP websites, and let users like me refuse the “upgrade” to HTTPS.
No it doesn't. HTTPS ensures that the data is not spied on or tampered with by those in the middle (so it does protect against what Comcast does), but does not prevent any other sorts of attacks (e.g. the server operator adding malicious files into their own server).
I should add a script to detect such things then, and if it finds one, display its own message to the user, to tell the user to disable JavaScript, with instructions about how to do so.