I'm not a new grad, but when I last switched jobs, I had to negotiate very aggressively to even get two weeks to consider other offers that might roll in before I had to make my choice. This was between a number of companies in the Seattle area, both big and small. I'm glad I negotiated to, because I got an offer that was >10% higher than my second best offer, and it came in about six days after the first (of four) offers I got.
I think the problem is that corporations value certainty as much as developers do, so they pressure people to make their choice now, so they can send rejection letters to other candidates, get the ball rolling on HR papework, etc. as soon as possible. For example, let's say an employer interviews 5 candidates, 1 per day, Monday through Friday. They conclude that their best candidate was Mrs. Friday, the second best was Mr. Wednesday, and so on. If they give Mrs. Friday a week to decide, and she rejects them, they might find that Mr. Wednesday has also accepted an offer in the meantime, and so is off the market as well.
That's why employers pressure you accept (or reject) them as soon as possible. They want to know whether you're going to accept or reject, so that they can move on to their next choice, before their next choice disappears as well. It's a way for the employer to minimize the opportunity cost of extending you an offer.
I think the problem is that corporations value certainty as much as developers do, so they pressure people to make their choice now, so they can send rejection letters to other candidates, get the ball rolling on HR papework, etc. as soon as possible. For example, let's say an employer interviews 5 candidates, 1 per day, Monday through Friday. They conclude that their best candidate was Mrs. Friday, the second best was Mr. Wednesday, and so on. If they give Mrs. Friday a week to decide, and she rejects them, they might find that Mr. Wednesday has also accepted an offer in the meantime, and so is off the market as well.
That's why employers pressure you accept (or reject) them as soon as possible. They want to know whether you're going to accept or reject, so that they can move on to their next choice, before their next choice disappears as well. It's a way for the employer to minimize the opportunity cost of extending you an offer.