You can say the same for any manufacturer of any industry : headphones, computers, cars and even tins of soup. You wouldn't buy one of everything because they're offered would you? Google, Microsoft and Samsung are just some of the main players in online storage. You only need pick one, possibly two maximum. The second one being Google as most android phones use Google services so a Google account is usually a good idea, however most just stick with a Samsung account. Just remember, the more accounts you have, the more of your data is floating around in the digital ether.