Is it accidental or deeply meaningful that the Higgs and the left-handed lepton have the same quantum numbers? Is it accidental or deeply meaningful that the Higgs and the left-handed lepton have the same quantum numbers?
Precisely, under $SU(3) \times SU(2) \times U(1)$:

*

*the Higgs has the quantum numbers: singlet under $SU(3)$, doublet under $SU(2)$, charge 1/2 under $U(1).$ Denote as $$(1,2)_{1/2}.$$


*the left-handed lepton has the quantum numbers: singlet under $SU(3)$, doublet under $SU(2)$, charge -1/2 under $U(1).$ Denote as $$(1,2)_{-1/2}.$$
 A: Well, do they?
In your ("modern", half-scale) conventions, $Q=T_3+Y_W$, you observe the lepton isodoublets with $Y_W=-1/2$,
$$
l_L = \begin{pmatrix} \nu\\ e^-_L\end{pmatrix}
$$
the isosinglets with $Y_W=-1$
$$
e^-_R,  
$$
(and, arguably, $\nu_R$ with $Y_W=0$). They all have lepton number 1, which is thus lacking from the Higgs doublet, with $Y_W=1/2$,
$$
H=\begin{pmatrix} H^+\\ H_0\end{pmatrix},
$$
and the conjugate with  $Y_W=-1/2$,
$$
\tilde H=\begin{pmatrix} H_0^*\\ -H^-\end{pmatrix}.
$$
The situation is somewhat analogous to the quark sector, whose color in the Yukawa coupling term is matched by the antiquark's; whereas in the Yukawas of the lepton sector it is just the lepton number that's matched by the antilepton's.
You then see that , e.g.,
$$
\frac{m_e}{v} ~    \overline{l_L}\cdot H e ^ -_R
$$
has the hypercharges (and hence charges) cancelling to 0=1/2+1/2-1, as required  of a Lagrangian term.
Likewise for a Dirac neutrino mass term,
$$
\frac{m_\nu}{v} ~    \overline{l_L}\cdot \tilde H  \nu_R,
$$
hence $Y_W= 1/2 -1/2 +0$. So, even outside the quark Yukawa, the SM has covered the entire waterfront.
You might, if you insisted, declare this fact not a coincidence, but a necessity, starting from the Y=0 right handed neutrino, so a Dirac mass term would force the hypercharges of the lepton doublet and the conjugate Higgs to be the same. But, to me, this appears like a shoulder-shrugging tautology, not a deep conceptual cornerstone...
