I think 99% of the time most of us developers would say we would rather create our own application to avoid using so many resources from the server. I’d say that depends because you would have to measure or at the very least know how long things would take. Meaning you can equally spend the same time doing your application versus using WordPress. I’d like to think it is “because we know better”. I’d say perhaps you don’t know WordPress well enough. And if you do then you already considered the limitations/database structures/optimizations for what you want.