Hi There,
depends of each case. Any way I think sons can't be ashamed to be naked in front of their mothers. My mother used to bath me till the end of my teenage years, about 19 years old. When she couldn't do it,that job was done by an old maid servant who had been my babysitter since my childhood. At that time, I was still uncircumcised and suffered of balanites ( irritation on the penis head and internal foreskin ) and still not operated because my pediatrician thought that to achieve a perfect "low & tight" circumcision, taking off all the foreskin ( mainly the internal one, with the langerhans cells ), necessary to resolve my chronic irritation on the knob, was indispensable the full growth of my penis around 20 y.o., as was done later on my 19,5 and a half years of age.She or the babysitter used to wash my glans and internal foreskin, using a kind of liquid soap and other antiseptics, drying both after, in order to difficult the growth of bacterias.
Those assisted baths continued till my circumcision at 19,5 of age. My mother didn't have, I suppose, the necessary confidence on me to do that washing perfectly, Any way she was obsessed with cleanness.
That usage never bothered me at all, even because, as usually, they gave a very good sensation of pain relief, and on the future, she or the same nanny did the same with my younger brother, who suffered of the same problem, till his circumcision several years later, exactly as happened to me.