I completely agree with this. I have commented on at least one post indicating that use of Suicide Girls content requires permission and attribution.

People work to produce their work, they should be paid for it. If you make money (Steem) for other people's efforts, you should pay them.

Whenever I use content from the web, I look for "public domain", request permission (where applicable), and directly cite my source. If any content creator asks me to remove their content, I happily edit it out of my post. This should be a general rule of etiquette when posting anywhere.