There is an unintended, potential consequence, in the long term, of near 100% spaying and neutering of domestic cats.
What might happen is that over generations the only cats being born are those from feral and stray cats because it is these cats who have avoided being spayed and neutered. All other domestic cats would have been sterilised.
If the only newborn cats are the offspring of stray and feral cats they are likely to have personalities which are less suited to living with humans.
These cats would have personalities which humans consider undesirable for domestic companion animals. They would have an inbuilt wariness of people and be highly motivated to hunt. Another aspect of domestic cats which is undesirable.
In short, the only cats being born would be genetically wilder than the average pet cat and therefore not ideal. Although the difference would be small, initially, over decades there may be a distinct difference in the quality of domestic cats compared to today.
It may be the case that in the long term future humans ‘undomesticate’ the domestic cat and the domestic cat returns to the wild again if you take this argument to its logical conclusion.
This might not be a bad thing because there are many failures in cat domestication. There is an argument that it should be undone.
My thanks to Dr Bradshaw who wrote Cat Sense.