Sometimes those places are just too lazy to take down the “hiring” sign or they want to build up their job applicant base because they might be hiring later or they want to be able to choose one person from the hundreds of applicants.
I worked for a very large company and saw what the recruiters see and make their decisions on: current title, current employer, last title, last employer, lenght of employment at each, major, school, name, address. From that information they would decide if they wanted to click on your link and open to see your resume (it took about 45 second to open the resume). Then they would look at it for about 2 minutes before they decided to print it out and then give the resume to me. I would then spend about five minutes or less deciding if I wanted them to screen you for an interview – sometimes more or less depending on how many applicants there were. I assure you, a lot of good people get missed.