Early on when I first began to carry a concealed weapon, I bought a shoulder holster at a gun show. Keep in mind I am not bashing gun shows or vendors that sell holsters, it is just that I bought something that sort of fit my gun. Entirely my fault for not knowing better but no one in the 16 hours of required instruction I took spent any time on carry methods or the necessity for having a good holster.
As in this story, I was going into a grocery store. I got out of my car and my new HK fell out of the holster, hitting the ground. It did not fire...lucky me. But it did put a scratch on my brand new gun.
The lesson I learned is once one decides on what method they are going to carry, make sure the holster is a good fit and made specifically for the model gun that you put in it.
And...further, with each student I endorse as having taught a Firearms Home Safety and Basic Pistol Course, I spend some time discussing holsters and the importance of protecting the gun, the trigger, and most of all, one's legs, family jewels, or what have you.