Investors are able to achieve ROI in other ways than curating content. Investment has existed for millenia, and ROI from curation only since Steem. Folks seeking ROI from curation rewards aren't actually investors, anymore than KKR are. They're profiteers extracting the proceeds of the business Steem conducts before that value increases the value of the underlying investment vehicle - the opposite of investing for capital gains.
Profiteers decrease the value of the investment vehicle by extracting that value. They reduce the value of Steem, not increase it. We don't want more of them, or more mechanisms they can use to extract the value of the content creators produce, because they harm those that are trying to increase the value of Steem by reducing the value of their stake.
Capital gains has encouraged investment for thousands of years, and built great enterprises because investors sought to increase the value of their investment. Profiteers only destroy businesses. Capital gains FTW.