1.She was sitting on the ground.She was out of breath, because she had been running.
2.Tom was tired when he got home, he had been working all day.
3.it wasn’t raining when we went out. The sun was shining. But it had been raining, so the ground was wet.

I have the same question about all these there sentences in past perfect continuous tense.

They are all finished actions,like she was not running. She was sitting. Tom was at home and it was not raining when they went. Why do they use past perfect continuous tense rather than past perfect tense?

Question

1.She was sitting on the ground.She was out of breath, because she had been running. 
2.Tom was tired when he got home, he had been working all day.
3.it wasn’t raining when we went out. The sun was shining. But it had been raining, so the ground was wet.

I have the same question about all these there sentences in past perfect continuous tense.

They are all finished actions,like she was not running. She was sitting. Tom was at home and it was not raining when they went. Why do they use past perfect continuous tense rather than past perfect tense?

Answer

The Perfect simple tenses focus on the completion of the action. We use a Perfect Continuous tense to focus on the effect of the action rather than its completion:

What had she done? She had run.
Why was she out of breath? Because she had been running.

What had he done? He had worked.
Why was he tired? Because he had been working.

What had happened? It had rained.
Why was the ground wet? Because it had been raining.