Let consider an $SU(2)$ doublet of bosons $\Phi =(\phi_A, \phi_B)$ which is described by the Lagrangian
$$L = (\partial_{\mu}\Phi)^{\dagger}(\partial_{\mu}\Phi) +a^2 V(\Phi^{\dagger} \Phi) -\frac{\lambda}{4} (\Phi^{\dagger} \Phi)^2$$
where $a^2, \lambda >0$. this Lagrangian is invariant under a global $SU(2) \times U(1)$. In order to require the Lagrangian to be invariant under a local $SU(2) \times U(1)$ transformation we have to replace derivatives by covariant derivatives induced by an $U(1)$ gauge field $B_{\mu}$ and vector bosonic $SU(2)$ gauge field $W=(W^1,W^2,W^3)$.
The continuation is well known: one observes that the field $\Phi^{\dagger} \Phi$ with respect the potential $V:= a^2 V\Phi^{\dagger} \Phi -\lambda/4 (\Phi^{\dagger} \Phi)^2 $ has non-vanishing VEV (vacuum expectation value), one chooses an arbitrary non zero vacuum value and breaks the symmetry in usual way.
One of the main motivations for this SSB (spontaneous symmetry breaking) mechanism is to explain how the obtained gauge bosons $Z_{\mu}$ and $W^{1/2}_{\mu}$ become massive bosons and one recognizes this property by observation that after symmetry braking the new Lagrangian contains terms $$\frac{g_W^{1/2} v^2}{8}W_{\mu}^{1/2} W^{1/2 \mu}\\ \frac{(g_W^2+g_B^2) v^2}{8}Z_{\mu}Z^{\mu}$$ which conventionally regarded as mass terms.
My question is simply is there any reason why one needs to introduce to principle of spontaneous symmetry breaking in order to obtain massive bosons (the mass is necessary to explain the short rangeness of the weak force)?
From naive point of view one might also try to extend the initial Lagrangian 'by hand' with 'mass terms' in gauge bosons. Why is this approach nowhere studied or compared with the conventional SSB mechanism which explains the massiveness of the gauge bosons?
What are the advantages? Is it simply easier to develop the theory in consistent way? Are the concrete calculations in most cases easier to perform?
