For most business line apps (i.e., the majority of code that's being written in the world) there's small chance a developer would be able to run a live demo of their code. If the code was freely available, it wouldn't meaningfully run without all the other connected systems and [semi-]live data - a live demo can exist (and often does, to be shown to potential customers or such), but it usually requires a bunch of dedicated servers and periodic work from operations team to configure & maintain it.