Use of "deshalb"

Question

Please consider the following sentences:

1. ich bin deshalb hergekommen, weil ich dich sprechen wollte.
2. Ich muss jetzt los, schon deshalb, weil die Kinder seit heute Nachmittag alleine sind.
3. Gleichwohl war das Gerät nicht sicher, und zwar deshalb, weil es gefälscht war.

What's the meaning of "deshalb" here?

Is it even necessary? Can't we just say:

1. ich bin hergekommen, weil ich dich sprechen wollte.
2. Ich muss jetzt los, weil die Kinder seit heute Nachmittag alleine sind.
3. Gleichwohl war das Gerät nicht sicher, weil es gefälscht war.

Or is there a certain meaning/feeling conveyed by combining "deshalb" with "weil"?

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Also if you could please help me with this confusing sentence:

Deshalb bin ich nicht hergekommen.

Which meaning is correct:

1. That's not why I came here.
2. That's why I didn't come here.

Answer 1

"Deshalb" in your above 3 sentences mainly act as reinforcement of the statement. It could be omitted without too much loss of information, but the sentences would be less "intense".

You second question is quite interesting, because the answer is: Both are correct.

Without a context and without a speaker who emphasis some parts of the sentence both translations are equally correct and even equally probable.

If e.g. the question was:

Why didn't you come? Tom was also here...

Then the answer would be:

Deshalb bin ich nicht hergekommen (because Tom was here I did not come).

If the question was:

Why did you come here? Because of the free food?

Then the answer could be:

Deshalb bin ich nicht hergekommen (instead I am here because of the interesting topic).

Answer 2

The word "deshalb" puts some emphasis on the reason and could be translated as "in particular" or "for the reason".

The sentences without "deshalb" are also correct, and the meaning is very similar but without the specific emphasis on the reasoning.

The sentence

Deshalb bin ich nicht hergekommen.

can mean both

1. That's why I didn't come here.
2. That's not why I came here.

depending on emphasis and intonation.

Without special emphasis I would understand the first meaning. If the word "deshalb" is emphasized with a rising tone it would be the second meaning. With emphasis on "deshalb" with a falling tone it would be the first meaning with emphasis on "deshalb" as a reference to a reason that has ben told before.

To make clear that you want the second meaning, you can write or say

Nicht deshalb bin ich hergekommen.

Answer 3

It is a bit overloaded here. Deshalb gives a causation that can correspond with anything in close proximity (it could be translated as because of this). So it allows constructs like [Some sentences giving the reason.] Deshalb [some consequence]. E.g. Ich wollte dich sprechen, deshalb bin ich hergekommen.

So deshalb might "point" to other places. In your examples it basically just points right next to it, which is why it does not really need to be there. But this use elevates the reason as something very specific. Ich bin hergekommen, weil ich dich sprechen wollte. could be read as I’ve come here, for multiple reasons, one of them is wanting to talk about something. But Ich bin deshalb hergekommen, weil ich dich sprechen wollte. conveys more of I’ve come here only because I wanted to talk about something.

In the second example this is paired with a schon, which basically states that this is the least important reasons. So schon deshalb, weil gives a sense that even the lowest reason is really important.

Regarding Deshalb bin ich nicht hergekommen?: Colloquially this can mean both things, depending on what emphasis you use. I’d say this would rather mean That’s why I didn’t come here. If you wanted to say That’s not why I came here you should rather say Ich bin nicht deshalb hergekommen. We can of course say Ich bin deshalb nicht hergekommen for the other thing.