I don't doubt you place IVs in sick patients, I only doubt those IVs make any difference. I am not very familiar with prehospital/EMT literature, and I don't know if any studies have been done, and I certainly don't have any hard data, but I do prefer when paramedics give aspirin, stick in a combi-tube, do basic stuff, and just rush the patient to the hospital instead of wasted time installing and IV on-site, giving fluids and what not. I've seen a great many "heart attacks" treated with fluids in full-blown congestive heart failure. This is anecdotal of course.
Again, for the 500 bolus, I am not aware of any literature to support it as a life-saving measure, and I do believe that if the patient is gonna code without a 500 bolus, he will code with a 500 bolus, too. We're talking of a previously healthy person suddenly dying here -- in those scenario fluid rarely makes a different unless its profuse bleeding, in which case 500 mL is not enough anyways.
The big problem I see with fluids, stethoscopes, IV benadryl, and the like, is that these things are DISTRACTIONS that make people waste their time trying to get a blood pressure when its obvious the patient's in shock (or equally obvious he isn't). A quick, focused history and exam + Epi + AED + Albuterol are the real life-savers and where the emphasis should be on.