You don't have to be a market domain expert, and even if you were, markets shift. Sometimes there actually was demand at the pre-seed stage, and by the time series A rolled around, incumbents have entered with competing products, or tastes have changed, or a million other things.

You have to put yourself in your (potential) customer's shoes. And more than that, you need to try and judge the founders' ability to do that, to see whether they can develop product relevancy as the company (and market) matures.

In other words, emotional intelligence is a valuable asset for early-stage companies.