Near miss

This morning, before heading off to a client's facility, I decided to run a few errands, one of which was deposit a couple checks. I parked in the front parking lot of my bank, a lot I normally don't park in because I'm usually going to both this bank and the bank next to it, so I park in the back lot.

The front lot has parking spots at an angle on both sides of the one way driveway down the side of the building. Cars pull in at a less-than-45° angle to park, then later back out and pull forward to leave.

When I was done and ready to pull out to leave, I watched the cars behind me until they pulled past, and waited for a pedestrian to either pause or pass. When she paused, and waved me along, I backed out of my spot, noticing two other cars had pulled into the driveway and were waiting for me.

As I finished backing out, the pedestrian started walking along my car to the right, and I shifted my car from reverse to first. I noticed movement out of the corner of my eye to the left. I turned to look left.

And saw a huge red truck reverse lights on, brake lights off, backing up, straight at me at a noticeable speed.

I laid on the horn, a horn getting a lot of use as of late, and held it there until the brake lights came on. I'm sure I startled the pedestrian, to my chagrin, as I hate when people honk when I'm walking by - horns are LOUD.

With the truck stopped, I pulled forward and drove away.

As I left the lot, heart thumping, thankful my car wasn't hit, I couldn't help but wonder, why didn't the car behind me, the driver of which had a front row seat of the impending disaster, honk? Why didn't the driver help me out by honking to stop both of us from colliding?