Offer and Suggestion

Hi Everybody,

Why don’t you let me cook the dinner tonight? This sentence was shown as an offerWhy don’t you just phone and tell them you can’t come? This sentence was shown as a suggestion.So what is the difference between in meaning between offering something and suggestion something?
Thanks in advance

It is to some extent a matter of perception, Emmoo, but:

The first is an offer for the speaker to do something.
The second suggests that the listener do something.

Thank you Mister Micawber. Now it makes a sense.