When I hire for a entry-level position, I usually end up with 300-500 resumes. First filter is college degree in the appropriate field. Second filter is 3.0+ GPA. That will cut things down to 50-100 resumes. I'll cruise through those resumes quickly. If there is anything at all that gives me a reason to throw them out, I will. Confusing resume, bad font, spelling errors, rambling cover letter, etc. -- I looking for a reason to toss the resume. That will take it down to about 20 or so. Then, I'll phone interview those 20 and cut it down to 5. Those five will come in for a series of interviews, top candidate gets the job offer.
The point is, when you have a lot of potential candidates for a position you'll look for any reason you can to disquallify someone. A poor GPA for an entry-level position is an easy thing to focus on, as the candidates have very little skills or experience.