Tree limbs die all the time. Normally when disease or damage kill a tree branch, it isn't a big deal because the tree is in a forest and probably won't fall on anybody or damage any property under it. In a city, you can't ignore a widowmaker. The risk of it damaging property or flat out killing somebody is too high, you have to pay to get it safely removed. Often this becomes "end-of-life removal" because it's deemed safer or cheaper in the long run to remove the tree entirely. So now you have a green mostly alive tree being chopped down because one of the limbs died, and everybody in the neighborhood thinks you're a tree butcher but nobody else wants to chip in to have it maintained.