Many businesses, especially software companies (my main experience) don't give employees any notice before firing them, downsizing, layoffs, etc. So what right do the have to expect notice when the employee is the one that ends it? Why don't they get a bad rep for the abrupt end of the relationship if that is a thing? It also depends on the company. Some companies want people to leave immediately as a general policy when they know for sure they are leaving.
That said I usually give at least two weeks notice when possible and there aren't extenuating circumstances. Sometimes they want that two weeks or more and sometimes they don't.