Is getting a lot of miles on a car actually bad for the car if the car is well taken care of?

Back story: I have been using my car to visit a guy who lives about an hour away from me, and my mother has said that I "don t need to be putting all those miles" on my car. It is a well-taken care of Ford mustang with about 125,000 miles on it, and I have not noticed any issues at all. Cars are meant to be driven, in my mind.
Is putting mileage on a care actually a bad thing, or is mother probably pulling an overprotective mother of an adult child?

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