Except that time and expense are factors. Figure on two hemp crops a year, compared to say 20 years for tree maturity. Plus logging and transport is quite expensive, but much of the processing for hemp could be done in the harvester before it even leaves the field.
Importantly, the paper industry is already mostly tooled to handle hemp pulp, which needs fewer steps in the process.
You can probably calculate that with legalization, hemp agriculture would have a production boom in the amount of acreage; so the first bottleneck would be in processing it.
Dream on, it does not hurt anything and is entertaining.
I am by no means opposed to canabis, but I sure hope we don’t begin growing enough to replace pulp wood, none of us would have anything except the munchies.