Sure, graphs are often better than tables.

That's not relevant to the point of whether tables should be sortable, if you already provide a table for some reason.

A more relevant task:

Given the data

    3  3.88
    5  5.45
    1  3.09
    2  3.39
    4  4.57

Can you tell if the columns are correlated? With sorting, you can, easily.