This excellent and very inexpensive Dremel compatible rotary tool is on sale again

No, just giving a literal answer to the question, “why not give credit/cash to the original artist/developer?”

I own Dremel-branded rotary tool, as well as other Bosch tools (Bosch now owns Dremel), because I have confidence in the quality and can afford the extra cost. However, I would have had no problem buying an alternate brand for a tool whose patent expired back when Eisenhower was President.

Dremel had his own ideas on this:

According to a newspaper article in 1968, Dremel often objected to being called an inventor.
“Inventors are complete innovators,” he would say. “They create things that didn’t exist before. I’m just an engineer. All I do is borrow an idea here, a part there, and build something.”