Most blogs are set up this way (I'd say "all," but that would be "all blogs in my experience"). There may be some blogging platforms that allow the blogger to choose to have results display in chron order rather than reverse chron order, but that would still be a blogger choice, not a reader choice.
Once a person has visited and explored a blog, when they return, they will want to see fresh, new content. In addition, if someone is writing a "newsy" blog, fresher content may have more relevance than older content, and the same would be true of blogs discussing tech how-tos, since technology is changing.
I do enjoy reading older posts on a blog I've just discovered, but I've never found it difficult to do so -- and for a blog with many entries, I usually read the posts that jump out at me and interest me most.
Many blogs, unless they're travelogues or something similar, aren't dependent on knowing a "back story." For example, I often visit recipe and cooking sites. I may hop around and look at different categories of recipes, but if I'm looking for rajma, I'm not going to care whether the blogger wrote the post before or after their entry on saag paneer.
If a reverse chron blog isn't appropriate for a particular writer, then they can find another way to present their material on the web. I personally find the reverse chron order just fine for my purposes, and I have an archives widget an calendar widget for anyone who may be interested in reading older posts. I also use tags & categories to organise my posts, and use pages for more "timeless" content. I find the web -- and blogging -- to be a very flexible medium, much more so than a paper book in which every page follows in sequence. Especially for reference works, html/xhtml is great -- and it isn't dependent upon either chronological order or physical order and can actually provide a better tool for the user. Though I admit that I do still love books and the printed page! :)