Lightweight tents

I was reading an article in Hike-Lite's blog from last year, and a thought crossed my mind:

If English law doesn't favour wild camping, why should lightweight tents (usually associated with wild camping) be considered mainstream?

Yes, I know that carrying less weight overall means you can, kilo-for-calories, trek further in a day. But if you are trekking between pre-booked pitches, you might not be traveling as far as walk-til-you-drop wild campers.