I think you've nailed it.

The reason these products don't focus on people is that people are hard. Hiring is one the hardest things out there, with often warped incentives on both ends re: honesty. Building a product/service to solve this dilemma in a way that satisfies all parties is probably even harder, and then on top of that you need a business model for pulling dollars out of the matching process.

It's much easier to just build a product that matches technology stacks, and it's not immediately obvious that it's the wrong approach.