In the mind ...
Buddhist hell only exists in one's mind
Here's an interesting story:
The Gates of Paradise
To me that story implies that:
- Heaven and hell can be experienced (or seen) now (or just a moment away)
- They exist as a consequence of (as result of) speech (by the monk) and action (by the soldier)
- They manifest in real life (including "physically") and not "only in one's mind"
Some people do have a view that the world can seem like hell, depending on your state of mind.
If hell were defined as "continuous suffering", according to that definition some people might see the current world as a state of woe.
... but not 'only' in the mind
But even if "hell" does exist in (or is perceived or experienced by) one's present mind (as illustrated above), it might be a mistake to assume that it only exists in the mind.
The suttas do describe hell realms -- for example Devaduta Sutta (MN 130) was referenced in the Wikipedia article.
I see nothing in that text which shows that the Buddha must have been talking metaphorically.
Theoretically I see three possibilities:
- The Buddha was speaking metaphorically (e.g. to persuade people to behave well)
- The Buddha was speaking literally (there is literally a realm like that)
- Something else
In any case, that sutta certainly appears to be referring to a state which may happen in the future, and is not just a state which is "only in one's mind" (in the present) -- it says,
I — by means of the divine eye, purified & surpassing the human — see beings passing away & re-appearing ...
... Or how these beings — who were endowed with bad conduct of body, speech & mind, who reviled noble ones, held wrong views and undertook actions under the influence of wrong views — with the break-up of the body, after death, have re-appeared in a plane of deprivation, a bad destination, a lower realm, hell.'
In summary you might find it useful to think of "hell" as something which "exists in one's mind", and which is taught to be a realm experienced "with the break-up of the body, after death", or seen "with the divine eye".
By analogy, if you see a photograph of something then it does "exist in the photograph": but it would be odd to say that it exists only in the photograph (the thing photographed may also still exist in real life).
FYI according to Wikipedia the Narakas are also described in Hinduism.
Within Buddhism (the article you referenced in the OP),
There are several schemes for enumerating these Narakas and describing their torments. The Abhidharma-kosa (Treasure House of Higher Knowledge) is the root text that describes the most common scheme, the Eight Cold Narakas and Eight Hot Narakas.
You're asking whether Wikipedia is wrong and why no-one changes it: but it doesn't seem to be "wrong" i.e. it is reporting or summarizing what's written in Buddhist literature.
The emphasis or people's interpretation of the Wikipedia article may be wrong, but so far as I know its content is more or less OK for an article that's titled "Naraka (Buddhism)".