Yes, the reason is purely technical. Shapr3D for mac is running on Catalyst, which is in a poor shape on Catalina, and not available on Mojave unfortunately. If we see significant demand for supporting older macOS versions, we will do it, but that would mean that we have to rewrite the UI from scratch, which does not sound like a reasonable investment, especially considering that most likely the M1 macs will gain very significant market share over the next couple of years. Another issue is that the performance of 3-4 years old macs are not even coming close to the performance of iPads (yes, seriously). So most likely we would have significant performance problems on those devices that are still on Mojave.