If one can see the Divine, why should one perform pooja


You are completely mistaken about pooja. The rule of pooja is only Shiva can worship Shiva. 
So first you place the names of the Divine on different parts of your body. You become part of the Divine and then you offer flowers and everything to the Divine. This is the actual and right way to do pooja, seeing the divinity inside. 
You are as much part of the Divinity as I am. You must know that godliness is in you too. God is in you as much as in me. If you are able to see well and good. You and I are not different, we are one. You should say, ‘I am a part of the Guru.’
Self-blame should be stopped and you should see that you belong to the Guru, to God and to the whole creation.
Why do I need to do pooja? Do I gain anything? No. It doesn’t matter whether I do or I don’t do but it is a custom. If I do then everybody else will also do. It is to lead by example. 
Lord Krishna also did and Sri Ram also did pooja and it is set in our tradition. So we continue the tradition like our elders did. If I don’t do, then why would anyone else follow? And how can I tell them also to do.
I don’t need to do pranayama, I don’t need to do kriya, I don’t need to do meditation and I don’t need to sit in satsang. But if I don’t sit, how can I inspire others to sit for satsang or to meditate? So, I also meditate. 
For me, eyes open or closed is all the same, but still I do. 
The same question Arjuna had asked Lord Krishna. Lord Krishna said, ’for me there is no karma. I don’t have to gain anything by doing karma nor will I lose anything by not doing it. But still - ‘varta eva ca karmani’ - I keep doing. Why? If I don’t do then people will not follow. They will follow me not doing anything and then there will be disaster.’
He said, ‘Just to lead by example I am doing everything, all the karma. So you also do work.’ Arjuna said, ‘No I am not going to do it.’ Krishna replied, ‘No, you have to do it.’
Arjuna again said, ‘Why? If karma is binding then why do you ask me to do karma? You say knowledge is freedom, then why do I have to act?’ 
Krishna said, ‘I also don’t need to do anything. But still I am doing everything. Then you should also do.’ 
Pooja means creating an atmosphere of Divinity and reposing in it. It is the chanting that is important. The chanting has all the vibrations from thousands of years. 
Like the tuning fork, when similar tune strings are there then they also vibrate. Similarly when you chant those mantras, your consciousness which is thousands of years old, somewhere the deeper layer starts reverberating. That is why when you hear those mantras, something happens in you. I have seen this all over the world, not only in India.
In the beginning when we say some chants, like ‘Om Namah Shivaya’, even those people who have no affinity towards Sanskrit or have never heard it before, when they chant this they say, ‘something happens inside’.
Our consciousness is very ancient, so the Vedic mantras have that power to touch the deepest layers of our consciousness. 
Now you can ask me, ‘why can’t we sing in German or French or Kannada or Urdu or Telugu or Assamese or Tamil?’ You can sing in any language, it doesn’t matter but the effect of these Vedic mantras are different. That is why they are called mantras, ‘Mananat trayatie Iti mantrah’. 
That which takes your mind across by listening to it or chanting it is called mantra. So these Maha-mantras have an impact on the consciousness that is why we say, ‘Om Namah Shivaya’, ‘Om Namo Narayana’.
Bhajans are different; you can sing ‘Radhe-Shyam’. Bhajans are different or any other language songs are different. But when you chant ‘Om’, it has an impeccable effect on the consciousness.