That assumes you know what you want and know what's reasonable/fair for the job and area.
Most people don't know. Even if they've worked a similar job in the area, doesn't mean they know what the current going rate is. Once when applying for a job I asked for what was basically my current salary plus $20,000. The hiring manager said something to the lines of "Oh, we can do better than that" and ended up hiring me at my ask plus ANOTHER $40,000. I had way undervalued myself and wasn't up to the moment on the latest in pay rates.
Needless to say I was lucky and that person was an excellent manager. But most people will not be so lucky and most managers are not that amazing.