PC Gaming

Sometimes you can get laptops with decent CPUs, but they only have onboard graphics
Sometimes you buy a system that physically can't house the GPU you want, but the board/PSU is proprietary, so you can't just change the tower/case.
Sometimes there are GPU heavy tasks that don't really rely on CPU that much, and you are using a laptop.

But the vast majority of the time, sticking a new card in your desktop is the way to go.

Marketing it to the gaming segment sells more units, but realistically these are great for full GPU loads like rendering or machine learning.

They became super popular with Apple fanboys because before they made the transition to Apple Silicon, they were effectively giant, expensive paper weights. In fact, the onboard Intel Iris GPU couldn't even draw Launchpad's animations without stutter when connected to a 4K display. This was a $2k machine with 1% GPU power. Literally. I think they were on par with Chrome Books.

The saving grace was the connectivity speed. Thunderbolt 3. Which meant you could eke out 60% of the card you're using provided it was faster than the lane could handle.

The article is just ad bait, because it's a pretty simple graph to calculate and graphic card makers have the industry (as is much of every sector) so price fixed that there are no "secret" finds anymore.

Laptops, or if you have multiple mid-range PC across the house (media center in living room, study PC in your room or working PC in your studio for convert video/3d render): you can move your portable GPU without reassembly.

Nowadays GPU are also kind of mobile AI, so you're not just moving gaming graphics but also a little offline chat/drawGPT, video converter etc.