Making the flights more frequent won't help if the marginal fuel cost on each flight exceeds the cost of disposable launch vechicles.
It may be worthwhile to have certain parts of a launch system be reusable, but the extra costs associated with such reuse are substantial. Given that weight is at an absolute premium on space flights, designing things for serviceability is expensive.
This is especially true with certain types of materials and systems which can be inspected as they are produced/assembled, but which cannot be effectively disassembled without destroying them. If you are trying to make a component reusable, it will have to survive repeated stress cycles, each of which is much worse than the stress cycle that must be survived by a disposable component (re-entry will almost certainly produce stresses on the reusable component. In addition, certain failure modes at certain parts of the mission may be acceptable in a disposable system but not in a reusable one (e.g. a failure of one part of the system which damages another part which is no longer needed for the current mission may be acceptable in a disposable system, but would make reusing the parts impossible).
To be sure, the lack of thousands of samples for QC analysis may make it hard to figure the best compromise among weight, cost, and reliability. Even here, though, disposable parts probably have an advantage. It's much easier to design a part to survive the fatigue induced by one or two heating/cooling cycles than to survive that induced by twenty or fifty. The more cycles a part will have to experience, the more possible modes exist for progressive weakening and failure.
If a particular type of component will be used on 100 missions, the cost of engineering that component will be spread over 100 missions whether that component is reused between missions or not. If the design/testing of a reusable component costs twice as much as that of a disposable component, that is a substantial increase in the per-mission cost of that component. If mission rates were high enough, this particilar aspect of the cost might be effectively amortized over enough missions as to be reasonable. On the other hand, the more missions a component has to survive, the more engineering it will require.