Otter you are correct. It is so we can get out of there quickly and in a safer manner. I have had numerous bad experiences parking in the lot. People park too close to the doors to get in safely. Some park in a manner that blocks our ability to turn out of spaces safely. The ambulance does not turn well out of the lanes in the lot with a lot of cars there. You have to swing wide and people do not yield or offer some space unless you have lights on (and even then they don’t always do it).
I try to park in ways that protect my crew as well as those around me. If there was a fire emergency while we were there, we would be one of the first to know and would be moving our rig to the other end of the lot to support our arriving crews.
Parking along the front of stores is a very common practice in emergency services due to quick escapes. As an example, in Baltimore County they have about 30-90 seconds to go responding from time of dispatch. While we have 6 minutes, we prefer not to waste any time due to some of the extended response times we have to the far reaches of our call area.