Within the same application and document, it can make sense. That's not what people are raging about though.

I think it depends on your workflow -- I'd tend to assume the receiving end has some formatting, and it would be best if the copied text was fit that formatting, rather than bringing formatting with it. Ultimately though it seems pretty arbitrary, I guess they just went with the default that benefits what they assumed would be the most popular workflow.

I dunno, we should all just use LaTeX to avoid these kinds of issues.

In a spreadsheet or word processor, you have Paste Special which allows you to be granular about what formatting, etc comes over with the paste.