  It is argued that the Weinberg-Salam model is the way it is because the most
general self-consistent effective field theory of massive vector bosons
interacting with fermions and photons at leading order coincides with the
Weinberg-Salam model in unitary gauge where the scalar field is replaced by its
vacuum expectation value. To support this argument the most general
Lorentz-invariant effective Lagrangian of massive vector bosons coupled to
massless fermions is considered. Restrictions imposed on the interaction terms
following from the consistency with the constraints of the second class and the
perturbative renormalizability in the sense of effective field theories is
analyzed. It is shown that the leading order effective Lagrangian containing
interaction terms with dimensionless coupling constants coincides with the
leading order effective Lagrangian of the locally invariant Yang-Mills theory
up to globally invariant mass term of the vector bosons. Including the fermion
masses and mixings and the interaction with the electromagnetic field leads to
an effective field theory which at leading order looks like as if it was an
$SU(2)\times U(1)$ gauge invariant theory with spontaneous symmetry breaking in
unitary gauge with the scalar field replaced by its vacuum expectation value.
