Why is it considered dangerous or could be fatal? So many other male animals are castrated.
Why do they need to come to my home/farm?
Birds cannot be easily or safely sedated like mammals so the procedure is traditionally done with the bird completely awake. Unlike mammals their testes are deep inside the body close to major blood vessels. This post shows what it takes to do it: https://www.backyardchickens.com/threads/graphic-pics-of-my-day-learning-to-caponize.675898/
Good luck finding a vet that can do this - there's very few that work on chickens, period.