The reason purity is good is because you've distilled something to its simplest, most essential and parsimonious form. It is only in this form that you can truly understand something, and only from this form do you have maximum flexibility to combine it with other pure elements to achieve any possible goal.

This is just as true for computer science as it is for material science, eg. good luck flying to the moon without first developing the table of periodic elements.

Yes, that sometimes this can take more time, and yes, you can often take shortcuts and mishmash something together that works well enough for many if not most currently pressing purposes. Only distilled forms are guaranteed to have enduring impact though.