  We point out the dominant importance of plasma injection effects for
relativistic winds from pulsars and black holes. We demonstrate that outside
the light cylinder the magnetically dominated outflows while sliding along the
helical magnetic field move in fact nearly radially with very large Lorentz
factors $\gamma_0 \gg 1 $, imprinted into the flow during pair production
within the gaps. Only at larger distances, $r \geq \gamma_0 (c/\Omega)$, the
MHD acceleration $\Gamma \propto r$ takes over. As a result, Blandford-Znajek
(BZ) driven outflows would produce spine-brightened images. The best-resolved
case of the jet in M87 shows both bright edge-brightened features, as well as
weaker spine-brightened feature. Only the spine-brightened component can be
BZ-driven/originate from the BH's magnetosphere.
