Pseudoephedrine is a key ingredient in making meth, which is why the sale of it is highly restricted in the U.S. and probably elsewhere. I don't think you can even get it over-the-counter in some countries.
Decongestants are mostly for things like constructing programming language grammars or studying for midterms, when being congested and dripping snot would particularly suck. I guess the stimulant effect doesn't hurt in those cases.
And I did make over a gallon of Herb and Garlic Broth using
this fine book. The author says it's good for colds. It required peeling and cleaning something like 50 garlic cloves, though.