I’ve never seen a 100k miles spark plug yet that was actually good, even in spite of the engine running apparently fine with no misfire codes.
Just like shocks and struts becoming weak with mileage engine performance also degrades a bit. Sometimes more than a bit.
The odds of something falling into the cylinder is near zero but the odds of plugs seizing in the threads are much higher.
Sometimes removal of the plugs will damage the threads no matter how careful you are. In a case like this the threads can be repaired with a thread insert although judging by posts on this forum over the last few years some misguided souls seem to think that replacing a cylinder head or an entire engine is required.