Of the three activities you mentioned, two are not based on copyright
royalties — speeches and performances are paid per event. Writing
articles is generally paid per piece, and there is often little
connection to copyright-based royalties. For example, much piecework
is written for magazines, whose income comes mainly from advertising,
plus some from subscribership. The subscribership money can be called
partially copyright-based in some cases, perhaps, if some percentage
of the subscribers would unsubscribe if they thought they could get
the same thing for free.

However, note that even though virtually all of most major newspapers’
content is available for free online now, many people still subscribe
to them — and newspaper publishers generally do not ascribe
subscriber loss to the fact that the publishers are making the content
available for free online, but to other factors.

Another example: I have an offer in my email inbox right now to write
an article (for a few hundred dollars) to be released under an open
copyright. This is paid writing: if I did enough of it, I could make
a living, yet clearly my fee is not truly royalty-based.

Despite the examples you chose, what you wrote is still true: there
*are* some creators who earn a living from copyright royalties, or
earn at least part of their living. The important question is not
whether there are such people, but whether there would be a *shortage*
of creativity without copyright. Based on what we’ve seen so far on
the Internet, and in the arts in an increasingly post-copyright world,
I think it’s pretty clear that creative production is in no danger.

We do not consider it a tragedy today that no one is paid to do
cashier calculations in their heads. There once were such people. It
was a prestigious position, in fact: highly skilled labor, and for
obvious reasons much in demand. The invention of the cash register
(and later the calculator and the computer) made this job completely
obsolete. Presumably the people who would have been doing that are
today doing something else instead.

It’s true that some people earn money through royalties today, but
they are not even a majority of creators. QuestionCopyright.org asks:
is this minority enough to justify a system that prohibits people from
sharing freely with each other?

These people seem to be ignored in http://www.copyrightmyths.org/myths#economics