"Going in and altering a creature's physiology for the sake of convenience was something I had to morally come to terms with."
I'll assume that 'convenience' in this regard specifically applies to altering a cat that will be an indoor-only pet. Especially considering a tomcat that will be outside, neutering is the only responsible choice, reducing not only procreation, but also horribly brutal fighting and miles of single-minded wandering in search of accommodating young ladies. ; ] It should be obvious that 'fixed' females guarantee a more tightly controlled population. The element of convenience for humans aside, it's also more humane for a 'kept kitty' to be sexually altered, as the urges and behavior that attend being a naturally intact cat will not disappear simply because the animal is an apartment or house dweller that hopefully never 'escapes'. Altering a pet that an owner doesn't intend to breed is an act of kindness. A mild digression: in my opinion, breeding is an ethical failure that eclipses any quandary about having a pet spayed or castrated.
The exponential growth of feral cat populations is mind-boggling. It's almost inconceivable how truly rapid and prolific unchecked feline reproduction is. Within a year, having up to three litters, one female cat can equate to 24 -- maybe less, maybe more. Let's assume that roughly half of her offspring are also female and then extrapolate the numbers similarly. Imagine one mother cat who has three girls, each of whom then births three girls of her own. That's thirteen female cats, possibly all born within a year, all of which will be sexually mature within a few months of birth. This is a hypothetical scenario where the mommas have no male kittens, though there are certainly plenty of boys born. The calendar keeps rolling and the inverted pyramid keeps widening. : / Many people are aware, while many more don't care.
With some help I'm currently taxed in trying to manage a small fleet of furry ones from my warehouse work site, totaling about 17. This is merely one location -- a small dot on the map. I wasn't the most responsible or proactive pet owner some years back, but I stridently insist that people have companion animals of whatever degree neutered. Letting unaltered Pom-Pom or Thunderballs roam freely -- or allowing her or him out for just one evening -- can dramatically increase the 'unwanted' cat population and exacerbate significant and substantial problems for the caring people who rather selflessly try to provide for the poor urchins.