Further debate involves the type of vest: tactical vs. personal, helmets, shields vs. none. As far as I'm concerned, the more protection the better. Ask any SWAT officer who's ever been in a deadly force confrontation. The importance of wearing armor is perhaps best illustrated by the unforgettable sight of the LAPD SWAT officer who raced to the 1997 North Hollywood bank shootout with his rifle, armor and helmet—still dressed in his gym clothes.
No Excuses
With the possible and rare exception of certain undercover work or inside duty that doesn't require contact with the public, there are no valid excuses for not wearing body armor. However, the "reasons" given for not wearing vests almost always have to do with 1) Comfort, 2) Cost, and 3) Denial.
1) Comfort. Yes, vests can be uncomfortable, especially in hot or humid climates. Or maybe you've "outgrown" your vest. But tell that to our military stationed in far less clement locations such as Iraq and Afghanistan. They never go out without their armor, helmets, and a heck of a lot more gear than most police (with the possible exception of SWAT).
2) Cost. Yes, vests can be costly, $500 - $1,000 each. However, there are ways to defray the cost, such as department issue, grants, and personal gifts to name a few. However, in performing a cost/benefit analysis, one can simply ask which is worth more: your life or $500?