My travel agency told me that one of the reasons for airlines piling up higher fuel charges to passengers instead of increasing the fares is there is no commision paid to the travel agency on the fuel surcharge!
Second reason is the fares would looked lower and more likely for the passengers to purchase the ticket until all the surcharges popped up and at that point most passengers would succumbed to the higher total price. Lastly it may be more difficult and takes longer to get approval from the authority.
They (the airlines) have it all worked out. I remembered BA made a huge profit from the fuel surcharge a couple of years ago!