I can sort of see your point - but trapping the same cat over and over and transporting this cat that is insanely scared out of its mind to the vet numerous times has got to be much more traumatic for the cat.
The issue with declawing is that it isn't removing a cat's nails. In order to prevent the nail from regrowing, the entire end of the toe from the joint on must be removed in its entirety - and cats walk on their toes. Because the procedure is so traumatic, it considered unnecessary mutilation and is basically illegal in 23 countries around the world. Even the American Veterinary Medical Association does not recommend it unless medically necessary for the cat.
Spaying and Neutering are considered necessary operations. There are many benefits to the cat, including long term health, behavior (if a pet), and it helps prevent more homeless cats - so there are social benefits, unlike declawing, which ONLY benefits the owner, not at all the cat. And while some spay incisions may become infected, there are usually no complications and no long-term problems with spaying and neutering - both of which are problems with declawing.
Ear-tipping is different than both of the above. If you've had your ears pierced, you're aware that there are very few nerve endings in the ear (unlike kitty's very sensitive paw pads/feet). So ear-tipping or notching isn't particularly painful, it heals quickly, and it prevents a feral cat from being transported to a vet more than once for a spay or neuter it's already had.
...and it doesn't affect the cat's hearing, and cats don't walk on their ears.