Why does Windows take so long to shut down?

My laptop is plugged in most of the time, and I’ve noticed that the battery level always stays at 99% and never actually reaches 100%. I’m not sure if this is normal or if it’s something I should be concerned about.

Will leaving my laptop plugged in while the battery level shows 99% cause long-term damage to the battery or the laptop itself? If so, are there any settings I need to adjust to prevent this?

Also, is there a specific reason why the battery level never reaches 100%? Should I be concerned, or is this just normal behavior for modern batteries?