I can think of 2 reasons why living in the moment is so difficult.
The first is distractions.
Distractions occupy the mind and take our focus away from the moment. The solution to this is to reduce distractions.
Distractions come in many forms. Be they environmental, or people or responsibilities. All these things can weigh on your mind and distract you from the moment.
The other thing is not knowing what we want.
When we’re doing want we want we naturally live closer to the moment. But if you don’t know what you want then you don’t know what you should be doing.
You don’t have to fully resolve these issues to live in the moment. But any movement from the status quo will make it easier.
And of course practice helps. It’s a skill like many things in life, that can be improved with repetition and practice.
But it’s worth the effort because living in the moment is the ultimate use of your time and your life.