It does not make sense to have a fixed salary decided upfront for a position. Candidates profiles rarely exactly match the job description. You might decide to take a risk on a promising junior candidates or decide for a more experienced candidates that you had in mind at first. Often, you end up also end up adapting the role the new hires to their qualifications which might differ from the original posting requirements.
The goal of a salary negotiation is to find common ground between what would make the prospective employee happy and what the company wants to pay to hire this specific person. If you are not willing to negotiate, you will surely hire even less people because most employment deal is a custom one.
Even if you post a range, you might end up going above or higher. The range is good to showcase what you would pay the hypothetical role and profile described in the job description. Depending on who's applying, there's always room for adjusting it to each specific case.