Have you ever been on the employer side? Because I have. I've been involved in negotiating and setting salaries for the last 18 years, for dozens of employees.
Your statement above has never been true in any of the companies I've worked. It would have been true if the employees were all perfect negotiators, everyone had perfect information, and we were quite weak negotiators and ended up being pushed until stretching.
In reality, hiring managers tend to have much more information - when hiring we know what we can hire others for, as well as what others have accepted, and what a typical employee will bring in. We also know much better what the market is like. You will likely get an offer that is low enough that some candidates will walk away from it.
On top of that, most potential employees are shit at negotiating. Most never negotiate at all - they take the offered number or leave it, but they rarely push.
But the first offer is never my best. Why? Because it doesn't have to be, and we'd be throwing money out the window if it was.
On the flip side, when I am the one seeking a job, I never, ever accept a first offer. I've never had a job offer I couldn't negotiate up. Anything from 10% to 40%. For most type of professional jobs you're likely to get a 5%-10% increase over the initial offer just from saying the offer is a bit on the low end, and asking if that's the best they can do.
At the same time, raises are hit and miss. If someone does something that really merits a raise, sure. But 90% of the time it is not obvious, and chances are we miss things that someone has done when we evaluate them that could have led to a raise if they, or their co-workers told us. This is part of the reason why people often get those "shock increases" when they apply for a new job: Applying forces them to update their CV's, which forces them to think about and formulate what value they bring. Most employees never actually tell their managers about that, on the assumption they know. They're very often wrong.
> Maybe through hard bargaining you could inch a bit more out, but to do it you have to introduce an unpleasant penny pinching theme into your relationship with coworkers and employer.
Frankly, I respect the employees that come to me and negotiate _more_, as long as they have done their homework and knows what they are worth, and can explain to me why. They are demonstrating that they understand their value to the business. Those are the employees that also tend to actively try to increase their value to the business.