Meditation can be difficult even when there are no external distractions because the mind is naturally active and can generate its own internal distractions.
When external distractions are removed, the mind may become fixated on internal distractions such as thoughts, emotions, and physical sensations. These internal distractions can make it difficult to maintain focus and concentration during meditation.
Additionally, when people are not used to the silence and stillness of a meditative state, it can be uncomfortable or even overwhelming for them, making it difficult to stay focused.
Additionally, for some people, the mind might be too active and racing, making it hard to focus on one thing. It could also be that the person lacks self-discipline and might find it hard to stay focus.
There is no one answer to this question, as the reasons can be different for different people. But with practice, people can learn to quiet the mind, minimize internal distractions and maintain focus during meditation.