Software (OS, browser, native apps, web apps, …) should make it easier to use plain text for both read/write clipboard operations. And probably should make it easier to prefer doing that.
I know that’s a lot more words to say a similar thing, but it avoids two problems with how you put it:
1. Not everyone will share your preference. (I’d hazard a guess that it’s a minority preference, albeit one I mostly share.)
2. It’s self-contradictory. The “damn text I copied” is not just an array of characters: it often includes formatting; it frequently interpolates other content that isn’t even text at all.
The latter is largely the basis for the former. You—and I, mostly!—might be after that array of characters. But many many people are after that richer content, and would be utterly baffled by copying something rich only to get that array of characters on the other side. And quite a lot of people would have little recourse to get what they want.
This is why the multipart clipboard solution is a pretty good compromise. It could be better! It could definitely accommodate the preference for plain text. But it can only be better for those of us with that preference, without regressing for the much more common preference, by keeping the common preference as default.
Part of the problem is a poor (or insufficiently DWIM) implementation of rich text copy-paste. If I copy text that has some parts bolded or italicised, that is indeed "the damn text I copied". But the fact that the source website happens to be 12pt blue Verdana should not override the fact that I'm writing an email in 11pt black Arial.
In many cases I do not particularly care whether an email is in 12pt blue Verdana or 11pt black Arial, I absolutely care about there suddenly being a big blue word in the middle of my otherwise-consistent paragraph.
So neither "rich text" nor "plain text" are really correct: often plain text is good enough, but sometimes it's easier to correct the rich text.
It's probably a hard problem to solve generically. Word has a little popup when pasting where you can select how you want that paste to be applied: Just text, text with its original formatting, or formatted text, adjusted to the document styles. So far I've used all three, so I guess there's no answer that fits all use cases.
I know that’s a lot more words to say a similar thing, but it avoids two problems with how you put it:
1. Not everyone will share your preference. (I’d hazard a guess that it’s a minority preference, albeit one I mostly share.)
2. It’s self-contradictory. The “damn text I copied” is not just an array of characters: it often includes formatting; it frequently interpolates other content that isn’t even text at all.
The latter is largely the basis for the former. You—and I, mostly!—might be after that array of characters. But many many people are after that richer content, and would be utterly baffled by copying something rich only to get that array of characters on the other side. And quite a lot of people would have little recourse to get what they want.
This is why the multipart clipboard solution is a pretty good compromise. It could be better! It could definitely accommodate the preference for plain text. But it can only be better for those of us with that preference, without regressing for the much more common preference, by keeping the common preference as default.