This Colloquium discusses the coherent electron transport properties of non-ideal quasi-one-dimensional carbon-based systems, i.e. graphene nanoribbons, carbon nanotubes and linear chains. Results are based on numerical simulations that implement Schröedinger/Poisson as well as non-equilibrium polaronic methodologies for the calculation of quantities relative to the conduction. Attention is paid on the role of localized or extended modifications of the structural and electronic symmetry within atomistic descriptions that go beyond phenomenological approaches. Three different types of perturbations are considered: (a) perturbations induced by defects/impurities in the atomic lattice, (b) perturbations induced by the coupling with the metallic contacts, and (c) perturbations induced by the application of bias. The objective is to elucidate the potentiality as well as the possible drawbacks of future all …