Not everyone wants to work for SV firm, much less in SV.
Even if your only consideration is your income, tax rates are a very small part of this. If you pay no local taxes but have to hire someone to clear the snow and blowdowns off your road, you're still out that money. If you have no town water or sewer, you have to pay someone to provide and maintain those services. Very few people consider only tax burden when choosing where to live. If that were so, people would be flocking to Kansas instead of San Francisco.
The larger point, though, is that some people will be closer to the decision boundary and $10k will move the boundary far enough to put them over.
New Hampshire still has municipal services despite much lower taxes. Of course, it varies but for someone making over $120k a year (many people in tech) the income tax is a huge lifetime burden that can likely eclipse any out-of-pocket differences.