In a hostage situation taking a shot may be dubious at best - what about where someone is already shooting anybody in range? If you were there and could shoot you would what to do what you could to make it count. SA would up your chances, especially with something like a shorter barrell revolver.
1. How frequently does that happen compared to just a face to face short range situation? 2. What is more likely to happen, snagging a hammer spur in the top of your pocket, or someone already shooting at long distance? 3. If you would actually practice until you master double-action shooting, how much difference would it make to your shooting? 3. How often does it happen in real life where a nut-job shoots random people at long range compared to randomly shooting them at short range? Seems like with a few exceptions, mass shootings are usually short range, well within double action capabilities.
Double actions are designed to be double action. However, it is a common situation where people will buy a double action revolver and do most of their shooting single action and never attain any proficiency with double action shooting. If single actions were all that superior for defense, we would all be carrying Colt Model P's.