Wikipedia defines "junk" as ---Waste, any undesired thing or substance--
When we really don't want junk we throw it in a big pile and put a fence around it. We call that a "junk yard". Rats nest there. Stray dogs will sometimes pass through.
Some people will dig through all that debris.Hoping that they might find somebody else's trash at a discount price.
Most of the time it's just junk. And it's dirty.
Can you picture a junk yard? Now picture junk food. It's no different.Trash.
Do not buy junk food. You don't need it. Your mate doesn't need it. Your children don't need it. There is no reason for it.