Oil old hardwood furniture without sanding?

I've got a quick question knowledgeable woodworkers. I have some hardwood outdoor furniture and a hardwood deck, both about five years old. I'm a time poor father of two and it's time for me up oil both the furniture and the deck. I want to know what the purpose of the sanding step is. Is it to spruce up old grey wood or does it have a functional purpose in making the oil penetrate further/better?

Basically, can I just wash and oil or do I have to sand? If I do have to sand, how much is the minimum I should do?

Sanding will remove some of the ingrained dirt washing cant removed, loose wood fibres and some weathered (green) wood otherwise if you just oil it, all this will be retained.

If the wood is deeply cracked sanding won't remove dirt in cracks anyway so it depends what you are chasing.
A pressure cleaner might also be the go.

If you want a pristine wood finish then the cracks have to be sanded, or cleaned, filled and then sanded.

If you re prepared to live with the dirt and cracks then just oil it.

Some photos of the wood might be useful.