Copies on a hard drive are no more permanent than copies on a Betamax tape.
And both are effectively permanent copies, at least until deleted, and as such both are potentially in violation of copyright law in many jurisdictions.
The browser has no idea if the content was intended to be temporary
Then maybe it shouldn't be actively inviting a user to download a permanent copy?
In many -- perhaps most -- jurisdictions, downloading and saving content off the Web will be an infringement of someone's copyright if not explicitly authorised, so the argument that the browser doesn't know the situation is weak.
And the potential for harm is pretty similar.
Do you really not see any potential for harm in inviting someone who agreed to temporary listening or viewing to save a permanent copy, in a way that is both highly visible and potentially confused with a facility provided by the site operator?
The only solution for site operators if that's the approach you want to take is to lock everything down as tight as possible with TPMs, causing extra work and costs for the site operator, potentially increasing security risks for the viewer, and removing any possibility of trust or turning a blind eye to minor cases that might have been useful for the viewer and tolerable for the site operator. As I've asked elsewhere in this discussion, how is any of that helping anyone?
The level of invitation, the level of harm, it's not that I don't see them, it's that they look exactly the same as you get with a Betamax machine. Insisting that a possibility of harm exists does not affect my point at all. And it's not a big risk, there's really no need to lock things down. Home taping never killed anything. If I had my way DRM on videos would be banned. It's not like it prevents piracy.
When Google introduced that button, I'm aware of some commercial sites that didn't use DRM and saw in the region of a 500% increase in the number of paying users grabbing whatever they could rather than paying for further views, continuing subscriptions, etc. Typically they soon implemented alternative methods of serving their videos, and the problem then disappeared again. It's a myth that such measures don't reduce piracy. They may or may not eliminate it completely, but piracy is not a binary problem and even eliminating a large amount of the casual piracy can be highly beneficial. Equally, even a significant incentive inviting casual piracy that was already possible but was not actually happening can be very damaging.
And both are effectively permanent copies, at least until deleted, and as such both are potentially in violation of copyright law in many jurisdictions.
The browser has no idea if the content was intended to be temporary
Then maybe it shouldn't be actively inviting a user to download a permanent copy?
In many -- perhaps most -- jurisdictions, downloading and saving content off the Web will be an infringement of someone's copyright if not explicitly authorised, so the argument that the browser doesn't know the situation is weak.
And the potential for harm is pretty similar.
Do you really not see any potential for harm in inviting someone who agreed to temporary listening or viewing to save a permanent copy, in a way that is both highly visible and potentially confused with a facility provided by the site operator?
The only solution for site operators if that's the approach you want to take is to lock everything down as tight as possible with TPMs, causing extra work and costs for the site operator, potentially increasing security risks for the viewer, and removing any possibility of trust or turning a blind eye to minor cases that might have been useful for the viewer and tolerable for the site operator. As I've asked elsewhere in this discussion, how is any of that helping anyone?