Not constantly, no. Orcs and goblins aren't everywhere and the others aren't common enough to constantly be raiding and attacking. It happens sometimes with orcs and goblins, but that's because there are PCs nearby to stop the raid or take revenge on the raiders.
The bolded part is very meta and gamist. Designing a world around that logic just does not work well, usually.
And while Orcs and Goblins aren't everywhere... there are a lot of them in many many many places. Looking at the FR wiki tells us that orcs general favored terrains are "Artic, Forests, Grasslands, Hills, Mountains, Swamps, and the Underdark" And goblins are said to be "common"
And those other creatures are rarer, but still not that rare, considering they are some of the most commonly encountered creatures in the game. And they all have in their lore blocks that they commonly raid and attack settlements. Particularly farmers for their livestock. If it happens commonly enough to be a common trait of the race in the racial write up.... it happens often enough to be a concern for the common folk.
None of those would be much of a concern. They're rare and most of those creatures wouldn't do more than eat a farmer or two and leave. That's not a town raid.
Ankhegs are based on Ants, they would destroy a town. And again, you are saying each individual thing is rare, but when you have dozens of rare things, one of them occurring is no longer a rare occurence.
Evil dragon attacks are rare in the extreme. They aren't stupid enough to attack cities. Demons and devils are even more rare, and don't have the numbers on the prime plane to form a raid. Evil societies don't typically raid, either. Perhaps kidnap someone for a sacrifice, but they aren't going to be taking over towns the vast majority of the time. Those rare times when they do, it's because PCs are there.
What city? We are talking frontier towns.
And, I don't know what kind of evil societies you are thinking of, but I was more referring to things like The Yuan-Ti Empire, the Drow Empire, The Hobgoblin Empire, you know, places known for conquering and taking dozens or hundreds of slaves.
Cults would be more likely to kidnap a single person for a sacrifice, and they would summon a demon which... doesn't really need numbers. Three Balezau could wipe out a town with no real militia in no time. Sure, maybe people running and screaming might escape, but far far more would die.
Also, again, you can't world build under the assumption "Bad things only happen when the players are there to stop them" it makes the world feel unrealistic.
Each thing doesn't have a 1% chance of happening. Nowhere close to it. As I pointed out, most of those creatures you mentions wouldn't even be raiding at all. Even at the less than 1% chance of going into civilized lands, they'd just nab a loner to eat and head away. More people would end up dead from murders than from these monsters.
I think you are far far underestimating how full of monsters your typical DnD world is presented as. Or how the lore we are given shows how often they attack "civilized" lands. And, you also seem to be under the impression that each threat has to destroy the town.
It doesn't. Go to India, and I'm fairly certain you will find villages with Tiger Walls or other defenses against tigers. It isn't because a tiger is going to slaughter the whole village, but because a tiger might kill a few people every few years, and people don't appreciate that risk.
DnD worlds are full of large predators like that, and opposing groups that would assault these frontier towns on a regular basis. Them not having any defenses against those common attacks is... beyond bizarre.