Those tuners cost money, due to unnecessary licencing for codecs, and with the cable boxes locked down there isn't an easy way to watch two stations anymore beyond having multiple TV's going or using a HTPC. It was mostly useful for sports and a related issue with Sunday evening broadcast TV occasionally getting delayed due to NFL bumping the schedule later. The only other use was neurotic channel surfing during commercial breaks, again obsolete with streaming and DVRs.

IIRC it was mostly useful for letting you channel surf during commercial breaks and using the PIP to know when to flip back, or making sure your VCR was chugging along making your Sopranos bootlegs.

Most people now use their TVs to watch on-demand, streamed content. But even for the people who watches broadcasting stuff, their phones now fill the need to watch something else during commercials.

it complicated the display UI, when the trend was toward fewer and more virtualized controls. It wasn't really easy to use.

You just want the hard inputs? what about the built in tuner? where and how does the sound mix? Output ch2 sound to a different external speaker and use the internal for ch1? etc.

Nobody really wanted it to the point of figuring out how to use it, or coming up with a control convention that spread to other users. For so many uses where "PIP" is useful, a 2nd display is much more useful, easier to set up and use, and more likely to be replaceable.

Next question is "What about 3D TV?" ... Many mature industries go through these cycles of marketing bullshit.

Decoding two 4k HDMI streams is hard. Decoding two NTSC/PAL streams was easy.

My new LG TV can split in two much like "Back to the Future 2". I also use Firefox's PIP like video pop-out. So I'd say it evolved, yet remains as much a niche as the original feature always was.

The only times I clicked on the picture in picture button in the browser is when I mistook it for the full screen button. I have no idea what I might want to use it for.

This isn't PIP on TV but I use the PIP feature on MacOS ALL THE TIME! It's so handy with Youtube videos. Just open in Safari, two-finger click and then two-finger click again to open the OS menu and go into PIP.

Hope this helps someone!

I didn't get the appeal of it in the first place - how can you concentrate on two things at once (watching one show and PIP with another one)?

OP is specifically referring to television. A very different use case than browser-based PIP.

Turned out to be far less useful in daily life than it was technologically impressive on the page.

We used it to watch sports in PIP and more engaging fare on the big picture.

I miss it. I would love to have it back. Guess I'm a minority.

The BskyB box which is given to users in the UK has it