  In this paper, we try to understand why the classical bulge fraction observed
in S0 galaxies is significantly higher than that in spiral galaxies. We carry
out a comparative study of the bulge and global properties of a sample of
spiral and S0 galaxies in a fixed environment. Our sample is flux limited and
contains 262 spiral and 155 S0 galaxies drawn from the Sloan Digital Sky
Survey. We have classified bulges into classical and pseudobulge categories
based on their position on the Kormendy diagram. Dividing our sample into bins
of galaxy stellar mass, we find that the fraction of S0 galaxies hosting a
classical bulge is significantly higher than the classical bulge fraction seen
in spirals even at fixed stellar mass. We have compared the bulge and the
global properties of spirals and S0 galaxies in our sample and find indications
that spiral galaxies which host a classical bulge, preferentially get converted
into S0 population as compared to pseudobulge hosting spirals. By studying the
star formation properties of our galaxies in the NUV-r color-mass diagram, we
find that the pseudobulge hosting spirals are mostly star forming while the
majority of classical bulge host spirals are in the green valley or in the
passive sequence. We suggest that some internal process, such as AGN feedback
or morphological quenching due to the massive bulge, quenches these classical
bulge hosting spirals and transforms them into S0 galaxies, thus resulting in
the observed predominance of the classical bulge in S0 galaxies.
