Artists who copy others' work without permission and pretend they created it all by themselves.
It's lazy. It's respectless. It's illegal.

It's not okay "because so many artists do it".
It's not okay "because these cases hardly ever go to court".
It's not okay "because the rules are not always clear".
It's not okay "because I don't mind if people copy my art".
It's not okay "because a drawing is different from a photograph".

It's not 'inspiration', it's theft.

(And yes, I did it too, but no, that doesn't make it acceptable, and yes, that sounds hypocritical, and yes I feel ashamed)