rns.recipes

https://reticulum.network/manual/understanding.html#wire-format

I can grasp the basic idea that it's used to determine broadly what a packet is for, exp 0xFA is a keep alive packet and 0x01 is transferring a resource.

I can also understand that since the context byte is part of the header rather than data, it isn't encrypted like the data payload of packet for single, link and group destinations and so is the only piece of information a transport node has about a packet's content.

But why is it important that every transport node has access to that information about what a packet is broadly for? Is there any good examples of this being necessary?

There's a lot of great example of why the context byte is needed in Transport.py ;)

Transport nodes need to be able to make some decisions when routing packets, for example whether they should try to validate signatures of link requests proofs, which is an "expensive", but necessary operation. There's many more great examples if you read the code.