I am not obligated to negotiate, especially if there is the possibility of competing offers. And because of this, a company's first offer very often is their best offer, and they never get a second chance.

The company is not buying trinkets at a flea market. It's trying to rent skilled labor in a competitive market. If you pay me less than I'm worth, I can usually find a higher bidder. So there is the price you can pay to get me to work for you next month, and there is a higher price you can pay to hire me and get me to stop seeking offers from other employers for the next N months.

And the possibility that someone would walk away rather than counter is the very thing that keeps initial offers reasonable for everybody. It is the very same principle behind unionized collective bargaining, without the cartel enforcer of the union. The Nash equilibrium is to always negotiate individually, because you will usually get more money, but the strategy that benefits the whole class (tech employees) the most in aggregate is for most of us to not negotiate at all, and to judge the first offer as the only offer, because that ensures that tech employers always have to open with their best possible offer, or risk losing the candidate entirely.

Fortunately for tech employers, tech employees don't have enough solidarity or a strong enough cartel enforcer to accept any common negotiations strategy.