"but they do come in handy in the case of a GPU failure or if you retire an older chip to a system that doesn't have a discrete graphics card"
And I recently discovered another advantage: an extra GPU - with different drivers - if you try to run an older, obsolete game.
I was recently trying to run the original Diablo 1 on my system, with a Ryzen 7 2700X and a Radeon RX 580. Unfortunately, it kept crashing, even when I tried everything that people on the internet said to try.
Then, I tried it on my laptop with a Geforce GTX 950M. Diablo worked fine. Then, I tried it on the same laptop, but told it to use the integrated Intel graphics. Diablo worked fine again.
So Diablo works on a Geforce and an Intel HD, but not a Radeon.
Now, if I had a Ryzen APU instead of my Ryzen 7, that wouldn't help, because that would be two Radeons. But for someone with an Intel CPU, having the Intel HD graphics means you've got two GPUs with two different graphics drivers, so that if one driver is incompatible with some software, there's at least a chance the other driver is compatible.
(In the end, I got Diablo 1 running on my desktop using VMWare Workstation Pro, with a Windows XP 32-bit virtual machine. I also tried Virtual Machine, but I had problems with its 3D acceleration. But VMWare Workstation Pro's 3D acceleration worked like a charm.)