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According to the fifth edition spell text, Wall of Force
[...] can't be dispelled by dispel magic.
Is there an in-world reason why this is the case (for any D&D setting)? Why can Wall of Force and Forcecage, almost uniquely among all spells, not be broken by Dispel Magic?
The answer is because of the varied and long history of magical force. Prior editions treated anything that was created with magical force uniquely, and there are still elements of that in 5e.
I'd put it at a stub rule or a rule by convention. It's something that the rules often strongly imply but never explicitly state as a literal general rule. In general, it's because "it's always been that way" and "similar effects work this way" and "if the game world is consistent with itself, it should work this way".
The convention or stub rule was probably closest to an actual rule in 3e, when the [Force] descriptor tag was applied to spells. If you read spell descriptions, item descriptions, and monster descriptions from prior editions, you'll find a consistent theme with magical force. Over time you'll begin to read between the lines and understand what magical force is supposed to be: It explicitly extends into the Ethereal plane, affects incorporeal beings as though they were physical, and force constructs are often so potent that you can't dispel them without a higher level spell. That's why disintegrate works, although, in some editions disintegrate is also a force effect so it may simply be a greater force.
5e continues some of this convention of force effects, probably because the spell descriptions were just copied over and then changed where they had to be.
Unfortunately, the only way to actually know these conventions is to read and play many editions and modules and encounter many force effects. And because it's just convention, not all tables will play that way and they may chose to play strict, literal RAW. It depends on if the goal of your table is to have the rules be consistent, or the game world be consistent. In my experience, the longer a group has played D&D, the longer they notice these unwritten rules and the more likely they are to follow them as unwritten conventions.
There are similar conventions that some tables carry on with, such as the border ethereal versus the deep ethereal, or psionics sometimes being is different than magic, or demons not having a fixed appearance, and so on. There are some very noodley things in the game that are echoes of historic rules that no longer exist or were just historic conventions where things are themed relatively consistently.
There are other examples where natural convention can intrude. For example, fireball, fire bolt, and fire storm explicitly note that they ignite flammable objects. However, wall of fire doesn't note that. Does that mean it doesn't? You could play strict RAW and "it only does what it says it does", but at the same time... fire is fire. Fire ignites things by convention. How about if we have an ability that lets us change fire damage on spells to cold damage. Those exist in UA content if nowhere else. Does a cold fireball still ignite objects? That's where we come back to the "if the game world is consistent with itself, it should work this way" and you have to pick between game world consistency and literal rules interpretation.
