I'd argue that most developers don't mind you modifying for personal use despite their license saying otherwise. That's just to protect them from having to render support to your modified version, as providing support to hundreds of different variants is not practical and will run the author's support costs up.
We cannot force authors to use a particular license model but rather give them advice when we see the terms are unreasonable. In this case, this is common practice, and is up to the author to provide clarity on their stance. The best way to achieve this is by asking them either through a private message or in the discussion tab on their file.