That is not uncommon, but neither is it the quantitative norm. A lot of authors are particular about the typesetting of their documents, and it does require a rendering environment.

It isn't unusual for a half-LaTeX half-something-else monstrosity to be rendered in a semi-custom environment. Especially if you're dealing with anything academic.

In those kinds of environments you may have a ton of assets, like graphs, that may either be large file-sizes, and/or re-generated during the rendering process from various large datasets. Those assets are not small, and may prevent you holding much more than a couple books on your $4 thumb drive.