"Chains can always be added if you think they will help."
Undoubtedly.
Although:
Sometimes they can become difficult to obtain if winter becomes more wintry than expected.
Sometimes they can become more difficult to install when the tractor is at the bottom of a ravine.
The principle involved is no different than the basic fundamental of a tractor: traction.
If you have it, the entire capability of your tractor is available. If you don't...