grammar - Confusion in using "due to"

I usually meet "due to" usage in a document or conversation, but in different ways. I did some research and found out that "due to" is adjectival.

Thus, the correct sentence should be:

The cancellation was due to rain

Instead of:

It was cancelled due to rain

But when I looked it up in Longman Dictionary, I found:

She has been absent from work due to illness

Can anybody tell me why the above sentence is correct?