Why do mice whose tails were surgically removed just after birth for generations, continue to produce mice with tails? (Foreign 2014)

A group of mice will normally breed, and every offspring will have a tail. Therefore, tail-less mice won’t be generated if the tails of these mice are surgically removed after each generation. This is the case due to the acquired nature of mice’s tail removal, which is not passed down to the next generations. The mice’s germ cells’ genes cannot be changed by removing the tail.