These nobodies sang for pennies in the streets, turned to prostitution for male customers, and sooner or later disappeared into the oblivion of the outcast. A great many ended up suicides.
And the famous ones, outside of their brief dazzling triumphs on stage, led lives full of distortion and depression:
Meanwhile, the years of superstardom were limited, because castrati tended to age badly: "Most of them become as big and fat as capons, with round and chubby hips, rumps, arms and throats." Even successful singers were shunned by many, their status as ambiguous as their bodies.
I recently became a fan of Andreas Scholl, a countertenor whose vocal range is said to be that of the alto castrato Senesino. Countertenors of course have not gone under the "little knife", a euphemism that only hints at the true horror of what the castrati went through when they were young boys:
... brought unsuspecting to a nameless place, screaming as he is held down for the operation, the wound cauterized with hot iron.
Countertenors did exist side by side historically with castrati, with the castrati apparently considered more illustrious and dominating opera especially. And it's reported that the castrati didn't quite sound like anyone else, including the female sopranos they replaced; there also would've been differences with countertenors (whose speaking voices tend to be low; testosterone, different type of vocal cord structure and development).
Countertenor Scholl and mezzo-soprano Bartoli render music with beauty, richness and power. Now after this article I wonder, what were the differences perceived in a castrato singing voice (of whatever range)? It seems the castrati in general were deemed to possess a prized vocal quality entirely their own, beyond individual differences in voice and musical ability; their listeners felt like they were hearing something not quite human.
They weren't viewed as human, not really. They were treated as instruments, cruelly shaped, forcibly carved. If the instrument cracked, you just threw it out; there were new ones to craft and maybe those would give you sounds you'd never heard before.
They were the products of a social, cultural and biological experiment, and a fascinating and disturbing example of how easy it is to adopt skewed and unhealthy cultural norms, and to excuse horrors in the name of (and for the sake of) beauty, art, or any number of other ideals.