First, I recommend that anyone buying real estate have an up to date survey whether or not there is a building on the land, but that's not your question.
If the land is part of a larger piece and has not yet been subdivided, then yes you must have it surveyed. A professional surveyor will also guide you through the subdivision process.
If the land has already been adequately described in the public record and there is no mortgage lender or title company setting forth a requirement for a survey, then it's your choice, get one or not.
I recommend viewing a current or at least reasonable current survey to make certain you know exactly where the lot lines sit. Every piece of real estate I have purchased had physical lot line characteristics at the site that did not match the survey and so in each case I was surprised to find where the real boundaries were. Having an accurate survey in hand is the only way to know exactly what you are purchasing.