Security is hard. Especially at the scale of those companies. Since they are big, they get a lot more hacking attempts. Makes more sense for bad actors to attack someone with millions of customers than your mom & pop store that might have hundreds, if everything being equal.
More and more people and compa ies wants to store things "in the cloud", (read: someone else's server). It is for the most part a good thing as it makes it easier to access, but it also opens up bigger and other attack vectors.
So, I think the number of breeches will only increase. Not always because the companies have bad security (though sometimes it is 100% that), but also because the attack vectors keep growing due to changed business decisions and user preferences.