Reach and people taking action are two different things entirely.
And the only thing that really matters is how many people are taking action.
That's why most of the platforms out there make it more and more difficult to figure out how many people are actually really taking action.
Because if they didn't, then it would become obvious that less an less people are actually really taking action, while more and more people are "just" being reached without taking any action at all.
Which would dramatically decrease ad spend on these platforms...