Hand drawn pixel graphics heavily relied on the hardware's color palette (and monitor properties) for dithering and 'lighting' tricks, and especially the C64 color palette is quite 'exotic' and didn't have overlap with other home computers of the time. You need to consider that essentially each pixel was carefully placed by hand to 'enhance' the limitations of the builtin palette through color bleeding with the neighoring pixels on CRT monitors.
Automatic conversion of images between different hardware platforms usually stood out as looking quite poor and a sign of a 'sloppy port'.
You see that the C64 palette has a much more muted, pastel look and does not map one to one to the CGA/default EGA palette. C64 has a lot less vivid colors, but it also has much better luminosity ramps which can make dithering look a lot better.
In addition, the C64 has restrictions on the number of colors you can use in the same 8x8 block which I don't think EGA had.
It takes an artist to turn a CGA/EGA image into a C64 image.
I think the C64 palette you linked has been "tweaked" by the artist who uploaded it, this is probably closer to the original: https://www.c64-wiki.com/wiki/Color
But your point is still valid: while IBM PCs and other machines of the time had a propensity for "pure" colors (cyan, magenta etc. - so 100% for one or two of the basic colors and 0 for the others), the C64 designers opted for more muted colors.
On my screen that doesn't match videos of actual C64's on actual CRT's. (It also doesn't match my memory of them, but that's a whole lot less reliable)
Videos of actual C64's on actual CRT's are pretty consistent other than brightness, though, so if it doesn't at least somewhat match those, the model is broken.
