Having the other verbs gives us more choice, more options, and thus the ability to make finer distinctions. I would liken it to a painter. In the basic colour groups of red, green, and blue there are thousands of shades. Each shade might be only subtly different from others, but having them available lets the painter pick exactly the right one for his or her needs.
So it is with words of similar basic meaning like the three verbs you mention. Each means something slightly different, as indicated by the excellent definitions you posted. Having them all available lets us choose whichever one best fits.
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