The real reason why you can't concentrate (stolen concentration)

What causes lack of concentration?
Experts say:
'It's the influence of smart devices.'
'It's because of bad eating habits.'
'It's because the quality of sleep is low.' etc.
There are so many reasons that I can't do it on my own.
I feel like I can't concentrate at all.
But the root cause is different.
If I could know exactly this
Immerse yourself in your work and feel more satisfied
You will be able to live your life.