The stock size Defenders have a wider Section Width and wider Tread Width than the skinny ones you're looking at.
Why would you want to put less rubber on the road when you're spending 95% of your time on the pavement? The tires are what keeps you on the pavement.
Grandpa says, come on out in the sand and the mud and have some fun sonny boy.
The stock size Defender M/S get the job done easily and are good highway tires too.