Question about the blue ? marks on mini-map

[JPM]

I know that you can rescue survivors when you go to those when they ping in your mini-map. What I don't get is that more than half the time when I do get there, it's just 1-2 corpses on the site with either a few freaks or marauders.

Was I just too late to get there to save them, or are some of them really just scripted to be that way when I arrive? Half the time I don't even bother with them anymore because:
1 - It takes me on a detour, away from where I'm actually going
2- Wastes my time and ammo since when I get there it's just corpses

Edit:
Thank you to everyone that answered, I have a better understanding of what they are now. Happy hunting everyone.

[harken23]

Sometimes it's a rescue, but it can also be other things like a horde (usually not a full-blown horde like at the mill, tho). Seems like a lot of them vanish before I arrive, too. I've had them pop up, a do a full nitros burn straight at it, and there's still nothing there. I guess sometimes you just don't get there on time.

[OtherWise]

from my experience, i belive that is the intended behaviour.
Meaning you can get a survivor or a body if you are late
in other cases its about past events, so its just about resource gathering (good for early game)
in other cases, its actually leading you to a trap (still remeber the day i fell in to one and got hang on a tree upside down).
In other words, its not always a survivor, its actually chance based on a pool of several events the game has.

[Nussy Snake]

Also remember, just because the blue blip disappears, it doesn't mean whatever the event is has disappeared. Just head that way where you estimate it might have been and see if you can find anything.

[CLeRiC670]

Correct you will regularly find those blue blips lead to corpses, no you didn't arrive late. If/when you loot all the stuff at those sites they will no longer ping your radar.

This is yet another reason why playing on the hardest difficulty is the best experience for this game, you aren't staring at the minimap while travelling because you can only make it pop up for a second or so when you use the vision/sense ability.

[.]

You can completely ignore them and still 100% the game. They are purely random scenarios that lead to enemies, loot, or traps.

[simon.pete15]

Yup. Basically the blue ? that pops up on the hud/minimap is 'a thing of interest' to you.