Quantum effects certainly do not disappear at macro scale. Everything at every scale aside from gravity is directly explained by quantum effects. The reason you

Quantum effects certainly do not disappear at macro scale. Everything at every scale aside from gravity is directly explained by quantum effects. The reason you don't see many weird things except in certain circumstances is related to 1. decoherence and 2. the wavelength that matter has. But everything is quantum even if you don't see weirdness. Certainty of probability and other "non-quantum" effects still fall within QM. For examples of macro scale quantum effects, see e.g. the Casimir effect and the HBT experiment aka photon bunching. There are many of them and scale doesn't really enter into it whatsoever. The key factor that underlies your question mainly is entanglement.