It's a matter of time, mostly. The big issue is that you have to design for it up front. Which doesn't necessarily mean you have to commit to it with the first launch, although that might be changing as SpaceX redefines what is market competitive. But you have to design the vehicle so that landings are feasible and sensible.

Most of the traditional optimizations for expendable launches de-optimize for reuse. The first stage is where there's the least sensitivity to mass, so first stages end up being the cheapest parts of the rocket with the upper stages being the most costly. They also tend to be optimized to have a small number of engines. The Atlas V has one engine on the first stage, for example. These things make reuse harder (can't throttle deep enough to make landing easy) and less worthwhile (you're reusing the cheapest part).

RocketLab and Blue Origin are designing their next gen rockets with reuse in mind, hopefully they can achieve success and get some market diversification in the reusable rockets field.