It's not how I prefer it, but rather "how it must be".
When you load a page of posts, the server has to access the database hundreds of times to build that page. Many database tables are combined together to make that one page you're looking at.
But what if you don't read the whole page? Then server resources have been wasted. Sure, it doesn't seem like much for modern computers, but multiply by dozens of users (including guests) and you have quite a server load.
Maybe I should have some kind of "Gold Membership" and enable various features for those who make a monthly donation or something.
You'll note that Guests only get 3 posts per page. I intentionally make it hard on non-logged-in "Guests" because I make it so easy to log in as a member. It's free after all. And Guests could be absolutely anyone -- banned members, bots from China, you name it. At least a logged-in member is a human being, however anonymous he is.