You don’t vote your own post automatically by default, so if you want, you can just vote your own post after posting it so that you will start with 1 vote.
However, not voting your own post allows yourself (and maybe the administrators and moderators) to see how many others have voted for your post. This can be useful in knowing how many others, beside yourself, agrees or are experiencing what you have posted.
You have created the post yourself, so it is clear that you would vote for whatever you have posted, but for other people who do not know who are the voters, seeing a default 1 vote or default 0 vote can help to differentiate which posts have been experienced by other people or not.