That is definitely not the result of a lack of regulation. The networks doing that are predominantly not public networks like Comcast, they're private internal corporate networks. The issue is they're a large enough minority that they can't be ignored. But that can't be fixed with regulation of public networks.
In fact, it's caused by certain regulations and pseudo-regulations like PCI-DSS, which require the default-deny policies you're referring to.
When my relatively small company announced that they were installing a Palo Alto firewall and that everyone needed to install client side certificates in order for web browsers to continue working, it set off major alarm bells in my head that led to one conclusion -- "No more non-work related web browsing at the office. No exceptions."
Most of my coworkers (albeit mostly those in support and not developers, but still people at least somewhat familiar with the way computers work) only cared that they'd still be allowed to visit Facebook during the day.
I was assured that "nobody was actively looking at employee web traffic" but that doesn't matter. They didn't even think it was a big deal to put this new monitoring in writing until I made a big stink out of it, and they added this to the employee handbook:
>Each of these communication avenues are subject to monitoring by the IT Security Manager, a supervisor, or the President. When using any of these communications, be aware that a business record is made, which is retained by the company and becomes the company's property. This business record may potentially contain sensitive personal information related to the sites you are viewing and into which you are logging on, including user/password information. If you do not wish to share such information, it is suggested you do not access those items using [employer]'s network.
I can see this becoming so bad that the only way to communicate freely would be to tunnel our stuff through TLS on port 443. (That is, doing what looks like HTTPS.)