But I don't understand the point of the shades, then. Why not go for the real thing? Why not use the exact same color, and it will not only "feel like few"? What's the actual advantage of using different shades (besides making the work of the web designer seem more difficult).
It lets you display more granular information. You can have light blue buttons with dark blue text, as well as solid blue buttons, to convey "primary" and "secondary" CTAs for instance.
You could try to display the same amount of info in less color, or even black and white (maybe outlined buttons, bold/regular fonts in the text), but color variation looks "good" to the majority of eyeballs.
