"Baseline" PAL/NTSC pixel clock is cca 8MHz, whereas "baseline" VGA (=640x480, not something you are used to nowadays) pixel clock is 32MHz, i.e. four times as much.

Or, if you want it in other terms, there are roughly 320x240 displayed pixels in a PAL/NTSC frame, which is again around four times less than in VGA.

Of course, SVGA, XGA and higher, especially on CRTs, are more and more demanding...

JW