First, employers do care about the rankings. Why do they care? Because they believe the highest ranked schools attract, on average, the most intelligent, hardest working students.
I agree. If an employer sees Yale on your resume they're going to assume that you're very smart, and very hardworking. Not bad.
Do you think the same holds true for specialty rankings, though? Based on nothing more than my own anecdotal experience, I've never seen an employer get excited over the fact that an otherwise unremarkable school is ranked high in some random subcategory.
Say I'm looking at two resumes. Author of Resume A went to an out of state school ranked 40, was ranked just outside the top 20%. Author of Resume B went to an out of state school ranked T4, was ranked just outside the top 20%. Assume I don't have a personal preference on the schools and I don't know either person.
I agree that if an employer has nothing else to go on they'll probably make the decision based on rankings. But how realistic is this scenario? Typically an employer is not limited to choosing between two out of state, relatively unknown applicants.
I agree with you that rankings do indeed matter, but I think the degree to which they matter dramatically decreases the farther down the list you go. At the offices I've worked at, a local T4 grad with personal connections would have a much better chance than an unknown out of state grad from a random top 50 school. I'm not saying that the ranking would be completely disregarded, but I'm not sure that it would be sufficient to overcome a lack of experience or personal connections, either.
I've seen people from T4 schools get hired over T1 grads because they worked at the office as an intern and did a great job. They were a known quantity, and the hiring attorneys felt comfortable with them. I've also seen resumes from candidates who attended higher-ranked, but not exactly prestigious, law schools summarily dismissed. Why? Because they were unknown quantities, and lawyers can be very risk adverse.
Now, if we include graduates from elite schools, the entire analysis changes. A Stanford grad will always get an interview, and probably get hired, based on pedigree alone.