Age: As people age, their bodies change and they may not be able to move as easily as they once could. This could be a factor in why Spears' dancing may have changed over time.
Injuries: Spears has suffered a number of injuries over the years, including a knee injury in 2004 and a hip injury in 2013. These injuries may have limited her mobility and made it difficult for her to dance the way she used to.
Personal choices: Spears has also gone through a number of personal struggles in recent years, including a highly publicized divorce and a battle for control of her finances. These struggles may have taken a toll on her physical and mental health, which could have affected her ability to dance.
Ultimately, only Spears knows why she may not dance like she used to. It could be a combination of factors, including age, injuries, and personal choices.