I am by far not the most educated on this topic, but my...

I am by far not the most educated on this topic, but my understanding is its to provide liquidity into the system (done through the banks). My understanding is that this helps the banks with their day to day activities and if they need to sell these assets its not done at incredibly discounted prices due yo liquidity.

Even though the banks have made huge profits I dont think its all kept in cash (what isnt paid out in divs) - most likely high quality assets (e.g. treasury bonds) which can very much be affected by liquidity.

Hope this helps you out a bit mate.