It's basic knowledge that you need in order to understand more advanced concepts. Want to know why beta-lactams cross-react in allergic patients to varying degrees? You need medicinal chemistry to truly understand that. Want to know how the different TKIs are able to overcome resistant mutants? Again, medicinal chemistry.
If you're wondering when the last time I drew allopurinol on command was, then you're right, it's never. Medicinal chemistry certainly isn't useless though. For me, at least, it laid the foundation for everything else I learned in pharmacy school.
So to answer your question, I use it all the time.