"Quilljar" expounded:

Pine trees are a crop just like cabbages. The lower branches are pruned
regularly so that the wood which will be harvested will be straight grained
and therefore fetch a much higher price - simple

That may be true if you're talking about a tended woodland, but in
this case the OP is talking about pine trees in general. There isn't
a little tree gnome running around the woods trimming branches.

A pine growing out in the open will keep most branches because there's
nothing competing with the branch for sunlight. In a woodland setting
there are always other trees coming up, so the pine puts more effort
into growing taller to stay in the sun. It's as simple as that.
--
Ann, gardening in Zone 6a
South of Boston, Massachusetts
e-mail address is not checked
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