Reasons
The few times I've been asked(I don't make a habit of letting people know I'm carrying)I tell them that I've always carried weapons-in my 4+ years in the military and 27 years in LE.I made a few serious enemies in my LE days.Most are out of prison now,so there's a reason.I live in a relatively small place in terms of people knowing each other.
When I'm travelling,it's a good idea too.I'm older and I don't plan being a victim if I can do something about it.I got a LEOSA credential from my former agency and with it I can carry concealed anywhere in the US except on a plane.I have to also carry proof of LE level qualification within the last year on the type(caliber)of weapon I'm carrying.
Retired LE people probably get less questions about this issue than most because they are presumed to be competent with firearms.
I personally believe any law abiding citizen should be able to carry anywhere anytime as long as they pass a proficiency test.That qualification even applies to active LE and it's a good idea to qualify periodically.
Shooting,unlike riding a bike,or some other things,is a perishable skill.