Because the presence of trees effects others. In an urban/suburban area they effect temperature, air quality, and rainwater runoff, among other things.

In a rural area in bulk, they effect air quality and carbon capture. Also erosion and water run-off. Clear-cutting a forest completely changes the local ecology, and not for the better, in a way that is irreversible.

We all need trees, and they take many years to grow to maturity. they should not be cut down en masse capriciously. And to do so effects others.