Some classification considers 3 types of cargo - bulk materials (metals, fuel); complex electronics; humans. The majority of weight is in the 1st type. Unless first two types have complex mechanical structure, where loads can't be distributed into supports - which is an important issue - the first two groups are candidates.
IT make no sense to build a dedicated launch system and non-reusable rocket to deliver a few 100kg max into orbit.
A Starship launches 150 tons reusable. That far cheaper and less work then building 500 Upper-Stages and shoot 500 of those rockets with a SpinLaunch system.
There is really no comparison in cost.
Maybe they could make the upper stage reusable but that would reduce the payload to and even more pathetic amount.
This system simply can not compete against reusable rockets.
But this launch system still needs the projectile itself to be a fairly complex rocket capable of delivering several km/s of delta V and of steering the payload onto a desired orbit. That still implies electronics and mechanical systems onboard even if you're carrying only bulk cargo.
Electronic chips themselves are rather good to withstand acceleration - can be packaged well. Mechanical systems for simple rockets could also be, well, simple - e.g. first orbital launcher of France used pressure-fed engine.
