Sunk cost fallacy. It didn't work out, the decision was made, they move on. I like that.

> so why throw away all that time?

https://en.wikipedia.org/wiki/Sunk_cost

Chiming in: indeed, the response is very dry, and raises suspicion. It states the obvious facts and then makes a boring statement, lacking any nuance of the conversation. It is not argumentative in the very least.

Time has been spend, yes. But the topic at hand is after so much time the conclusion to abandon this path is justified.