Pretty much only to confirm a certain tire being over worked and that's just by feel, on dirt most just look at condition of the tire or more than temps look at pressure gains as soon as kart leaves the scales.
I'd agree. You can tell by feel of the hand after a race which corner of the car is working the hardest. For some, a thermal gun is easier, and gives you a "recordable" set of data rather than just a "feeling." I get that. We monitored tire temps when doing tire testing very closely. They revealed some interesting things, but probably very little that transfers to a night of racing.
With that said, more data is not a bad thing....just knowing how to use it is the key.
Tire temps are only a guide. If you take tire temps over a period of time, establishing a pattern, they can be a guide to when you are doing something right or doing something wrong. F1 teams go to a lot of trouble to acquire on track tire temperature information. I find that very interesting.