It's easier to prescribe than to explain why not. (It takes less time, it's expected, it's someone else's money and diagnostic confusion from partial or inappropriate treatment will likely be someone else's problem.)

Antibiotic resistance may be the number one problem facing the medical community, according to several major medical organizations or associations.  "Since 2000, two new classes of antibiotics have been approved for use, compared with none between 1970 and 2000, and 10 between 1930 and 1960." Practitioners may not have "effective antibiotics to treat all patients in the future.

According to Ron Dagan, MD, director of the pediatric infectious disease unit at Soroka Medical Center in Beer-Sheva, Israel “Pediatricians are still using antibiotics much beyond what is needed, and they must remember that some are worse than others at driving resistance."  Among the worst is Azithromycin, which is a "very popular drug because it is long acting. It can be given in three doses, sometimes maybe even one dose, to get rid of the susceptible organism, so a lot of pediatricians use it for almost everything.  Cephalosporins are another offender, while amoxicillin and amoxicillin clavulanate have much less of an effect on antibiotic pressure.

The “ESKAPE” pathogens (per the Infectious Diseases Society of America) cause the most U.S. hospital-associated infections and are resistant to many antibacterial drugs:

Enterococcus faecium.

Staphylococcus aureus.

Klebsiella pneumoniae.

Acinetobacter baumannii.

Pseudomonas aeruginosa.

   Enterobacter species.

Of these. MRSA - Methicillin Resistant Staphylococcus Aureus and S. pneumoniae remain the most problematic.

Unfortunately, we are seeing fewer and less effective efforts that promote judicious antibiotic use, in part because the infectious disease specialists, [today] are spending more time on grant writing and lab research with less teaching of junior physicians and minimal patient care.”

Source: "Are we entering a post-antibiotic era?"  in Infectious Diseases in Children August 2009