Unlike the lone survivor aka us - Preston Garvey is not a lone survivor of the minutemen, he's the lone complainer who never did anything and outlived everyone due to that.
As he will repeatedly tell you / do - Preston is:
1- a hypochondriac who coughs at everything and can't stand the smell of the wasteland - after living in the wasteland his entire life.
2- a nyctophobe who constantly reminds you he is afraid of the dark - how he got to be a minuteman when darkness is apparently his kryptonite is amazing
3- brainless raiders will cobble together pipe weapons in what would normally be a Macgyver episode of gum, string, a pipe, and some matches, but Preston constantly wonders why I am picking up 'junk'
2+2 does not equate to logical conclusions in wonder-minuteman's head
4- last but not least, as much as people comment about dogmeat - who I love because he's loyal and doesn't judge me for my stealing, drug use, and stabbing people randomly - he hardly ever gets in my way, Preston is a walking, talking obstacle course.
If I didn't need to keep using him for awhile longer to get each companion affinity perk, I would dispose of his body in the nearest super mutant meat bag and blame 'raiders' when anyone asks where he went.