As a result, resilience isn't great.
Bombers and logistic planes have redundancy.
Depending on how fast the plane is going, "good chunk" might be a hilarious understatement too. Hitting an object at 1000mph imparts 4x the damage compared to hitting an object at 500mph.
If you want to see an example of a durable military aircraft, look at the A-10:
(Hit by a literal bird, still flying: https://www.nbcrightnow.com/news/a-10-warthog-hits-bird-at-r...)
(Hit by idk what, giant hole in engine, engine on fire, still flying for an hour back to base: https://theaviationgeekclub.com/heres-another-story-10-warth...)
Anyways, that's a military plane designed to get hit by... stuff... and as a result can take bird strikes. But its max speed is like 400mph and it would get absolutely wrecked by any serious opposition from fighters. The more resilient you make a plane to birds, the more vulnerable it is to missiles, per unit price. And missiles is kinda the point of the whole endeavor.
Some helicopters have a single engine. Most have 2. They are still unreliable death machines, and arguably 2 engines makes the problem a bit worse (more moving parts). They are (sometimes) more tolerant of a single engine out, of course. But transmissions are often the weak spot with helicopters.
Single vs Dual has many factors, not just reliability.
A single engine failure on a SR71 (if I remember correctly) resulted in a airframe loss and ejection at relatively low speeds, and one at full speed would likely result in a complete crew loss on top of it - and it has dual engines. Think catastrophic near instant destruction.
Sometimes you just need more power than a single engine (with current tech) can provide in the space you have available, for instance.
Sometimes, like an A10, you really do want something that can take a massive beating and keep going.
A B52 can lose 2 engines with no issues, and theoretically up to 4 and still be controllable (depending on the distribution of the lost engines). But that isn’t because it needs reliability, but because it’s got 8 engines because it was designed to carry a metric shit ton of explosives, and it only had 60’s era tech jet engines.
Modern jets usually use 2 (much more powerful) engines for similar or even larger payloads.