No, you don't need to convey a moral. And probably shouldn't.
Many blog posts are just informative and explanatory about what is going on in the world, from your point of view. The scope can be global (like global politics, or climate change effects, etc) down to private life; say you want to describe the cute kids next door playing pirates in the yard.
There doesn't have to be a moral, it just has to be interesting. If you are using it to practice writing, you may write short-stories, or even write a critique of a published book, or write about technicalities of writing with examples of books.
In fiction, there is very little gain in moralizing, or trying to sum things up into a moral, unless your readers are little children. For teens to adults, if readers don't get the "moral" you are trying to convey, you aren't writing well, and a final "moral" that disagrees with everything they just read (from their point of view) can seem like a bad ending. It's kind of like telling somebody a joke you made up, and the explaining to them why this joke is funny.
The end of the book and the last lines should leave the reader immersed in the story world. A moral talking about the book will break that immersion, and seem out of place. And finally, just the fact that you've written a book to illustrate a moral breaks the immersion even more, because it makes the story feel contrived to serve this outer purpose, so the story feels less real to the reader.
If you are writing a blog to practice writing, practice without a moral, and write to entertain. So your blog entry might have a theme or topic, and might illustrate a moral, but Leonardo Da Vinci didn't paint footnotes on his paintings telling us why he painted them or what he wants us to see. Let your work speak for itself.