Why is it important that the baryon and lepton numbers of an interaction are conserved?

Conservation Laws are useful because they establish fixed rules that physical interactions must follow, which helps physicists to better understand these processes. In particular, they provide a picture of what should and should not be possible to achieve in a particular interaction.Baryon number conservation is therefore very important as it can be used to determine the possible outcomes of particle interactions. For example, it shows that the proton is the only stable baryon, as it is the least massive and therefore cannot decay to any other particle without violating baryon number conservation. Similarly, lepton number conservation has been used to explain seemingly anomalous experimental results. For example, the decay of a neutron into an electron and a proton should provide the produced electron with a well-defined and known energy. However, observed electrons from this decay process have a range of energies, seemingly violating the conservation of energy and momentum. This can be resolved by applying lepton number conservation, which requires there be an antilepton to balance the electron, which turns out to be the electron antineutrino.