We suspected that the setup for the tent was just too much hassle, or that they wanted to change the format of the show to keep it fresh, but it turns out that the reason behind the tent being ditched could actually be a very simple one. See the following Reddit post below.
The poster explains how while at the filing of one of the tent segments of The Grand Tour for Season 3, the filming was constantly being stopped due to planes flying over from the private airfield. It’s very simple, but explains a lot. As you know, the tent and filming causes a lot of disruption to the surrounding areas: extra traffic, fast and loud cars, more people… and because of this the team would surely find it very difficult to hire out a different space for the tent to be erected.
So, to remove this added issue, they have simply decided to remove the tent segments and focus solely on the road trips. We’re perfectly happy with that, but we’re sure that some fans will be disappointed by the fact they’ll never get to see a live show.