Have you ever been playing a #videoGame (likely real-time) and finish a ranged combat encounter, only to wander through the arena finding set-pieces and interactables that were supposed to be used during the fight?
Things such as:
-- A hanging object that could be dropped on your foes.
-- A big pipe that could be damaged to spurt obfuscating or damaging steam.
-- A drawbridge or doorway that could be lowered, thus reducing the threat vectors.
You may have felt disappointed, but probably not as disappointed as the #levelDesigner who set them up!
So that's happening here?
Well, the designer has created the arena and set up the space with lots of goodies for you to play with - but has forgotten, or not grasped, the typical behavior of players in fights.
The typical behavior of a player in a ranged, real-time, combat encounter - is to hunker down at the narrowest choke point (often a doorway) that offers them excellent cover, and STAY PUT.
And why wouldn't you?! It's probably the safest place to be. You know the area you've come from is free of baddies, and you can restrict your threats to your field of view through the door.
Not to mention - once combat is begun, players become very tunnel-visioned - focusing exclusively on the positions of enemies. Less important features like objects in the environment, interactable objects, or even pickups, become functionally invisible*.
And this leads to a videogame cliché you may have wondered about -
Why do enemies hide behind red barrels?
You can probably see the answer already - it's because you, the player, are likely barely paying the explosive barrel any attention at all (it's not an enemy), but it IS supposed to be a fun feature for you to take advantage of in the fight, so you can feel clever and tactical.
So designers put cover markup next to, in front of, and behind, the red, explosive, barrel. That way, A) your attention is drawn to the barrel due to the proximity of the enemy, and B) it gives you a clear use-case for the barrel without the ambiguity of "is that enemy close enough for the explosion".
Bonus, your wild aiming may catch the occasional red barrel anyway, even if you didn't recognize it, providing you with fun explosions and effects, and making you a little more likely to seek them out in the future.
And of course, red barrels are so ubiquitous, that you'll be seeking them out in future games too! They're a cliche, a staple, and a well loved trope, for a reason!
(* Most players, most of the time, only see the enemies - until something changes to mix up their order of priorities. If they run out of ammo, suddenly they can see pickups again! It's all about how much you can focus on at a time.)