Shader variant precompilation has been a nightmare for projects which utilise runtime loaded assets, or assets which rely on scripts to enable/disable shader keywords.
The short fact is you can't always anticipate every possible shader use - Shader Variant Collections, don't always solve the problem either (some effects simply require a large number of variants to be packaged). At this very minute, I'm compiling a project to try test if a missing variant is the problem - it's taken 15 hours, and currently has over 40gb in the projects shader cache (... and counting).
Finally, the precompiled shaders can occupy significant space - the Standard shader often compiles to many megabytes for us, and it is on the simpler end of the spectrum.
Please at least, provide the option to indicate a shader should be compiled at runtime on demand, and not rely on precomputed shaders.