The answer there is probably to let the users pick their own tools too. If someone wants to chart data in your system for a PowerPoint presentation, the answer might be to give them a CSV export, instead of building a chart drawing tool into your application. (Of course, that assumes that your monetization strategy doesn't rest on restricting access to your data...)

x = {1..5} and y = {3.0982, 3.3928, 3.8838, 4.5712, 5.45500}

can you tell if that's linear, quadratic, or something else? Probably not. But if I show you a graph:

http://www.wolframalpha.com/input/?i=.0982*x**2%2B3

it becomes pretty obvious. A table is not the right way to display this data.

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