I'll disagree. This is not difficult, it's math. Yes, the feature would require allocation of development resources, but tangent snapping comes down to mathematics and/or algorithms that are pretty well-defined, with precedents in both graphic design software and in other areas of computer graphics.
Whether it's about Adobe or Affinity supporting or not supporting this feature, it all comes down to resource prioritization. This particular piece of work isn't rocket science, but does take up limited bandwidth for UX design, implementation, testing, etc.
For my part, I've also had need for snapping to tangents in my work, enough that I bought Astute Graphics' plugins to support that workflow.
So I'll add my +1 to support for snapping to tangency, which ultimately ends up covering snapping to path tangency and becomes a form of object collision snapping.