This "show me data" line works well in debates, but not in the real world. You often don't have the time or ability to wait for data to roll in, do a study, have it peer reviewed, and then make a decision. In real life you constantly have to make decisions under uncertain conditions with limited information of unknown quality. And that's the situation we're in right now.

We can send the kids back to school with no vaccines, no masks, no precautions, and say "We don't have any data that this thing is dangerous for children". The obvious problem there is that we don't have a ton of data in general with this variant. So, if we're wrong about the danger, we risk harming a lot of children while we dutifully wait for the data to roll in.

This is the same reason that most women (and many men for that matter) will cross the street late at night if they are on an empty street and see a large man approaching them. They have zero evidence suggesting that the person is a threat, but the cost of being wrong in such cases is very high. So, having limited data, they tend to take a very cautious and conservative approach and cross the street. In our case, just change, "Cross the street" to "Wear a mask".

This comparison is far from perfect, but you get the idea.