Why is Tropicana kept and displayed refrigerated in the local shop/supermarket whilst similar brands like Del Monte are mainly displayed out of the fridge?
some are fresh juices, and some are treated to be 'long-life', in the same way you can buy fresh milk, and long-life milk. once they're openened though, you have to keep all of them refrigerated
ethandron is right. The juices sold at room temperature have all been pasteuirised and vacuum packed in order to kill and prevent further microbial and fungal growth.
The juices in the fridges are almost as fresh as the "freshly-squeezed" types and contain no additives. They have to be kept in the fridge or they will go off in no time at all. This is the reason why they have shorter shelf-life and use-by dates than the juices sold elsewhere in the shops.
The ambient product juices will have Best Before dates on them which can be for a few months whereas the chilled are more likely to have a Use by date of a few weeks at most.
A lot of the ambient ones are made from concentrate with water added to reconstitute the juice.