HR people are valuable in a company. But their role is to get resumes in front of the real decision makers, and to take care of all the stuff like W-2 forms and whatnot nobody wants to deal with, not make decisions about who to hire.
It seems weird to me that so many tech companies have adopted this particular Big Corp characteristic, because it's certainly not a universal phenomenon. A tech company is not Wal-Mart. Its hiring process should not be structured like Wal-Mart. People are the lifeblood of a technical company. Tech companies should not therefore look to Big Corps who just hire large amounts of unskilled labor. They should look, instead, at how hiring is done at a consulting company or an investment bank, companies that are also reliant on skilled people as their most important asset. At those places, from your screening interview forward, you are only evaluated by someone on the business side of things. It might be a junior analyst or a senior managing director,[1] but it's someone who does the work that makes the business money. HR's job is to get good candidates in front of those people.
At least in my experience, start-ups and very small tech companies do this right, out of necessity. Where I used to work, interviews would involve talking with a few line engineers, then the VP of Engineering, then briefly the CEO (who was a technical person). I think as companies get bigger, they feel like they need to adopt the Big Corp model. But this start-up model of hiring scales just fine to companies of 500-1,000 technical people if you're willing to create a culture where everyone, especially the top technical leadership, is personally invested in hiring and devotes a reasonable amount of time to evaluating people.
[1] Anecdote: I once had a screening interview conducted by the managing partner of the D.C. office of a major law firm. He flew out to Chicago for a day every year to talk to prospective entry-level candidates.