Why can't we have .Add and .Remove aswell as += and -= operations after all its just a collection, I was rather supprised that this method wasn't actually available for adding event handlers.
One of our design goals is not to have more than one way of doing something (in contrast to Perl's tmtowtdi). If there are two different ways of doing something, developers need to learn both ways and understand that they are equivalent. That makes their job more complex without any real benefit.
Another area that this shows up is on delegates. Since C# has a special syntax for invoking delegates, we don't let you call Invoke() directly.