I beg to differ, if it weren't for operational (and finance) lease, many airlines would not exist.
The dynamics and reasons for leasing are various within the airline industry. We have the luxury of not having too many "surprises" like pandemics and terrorist attacks which decimate passenger demands. Leasing accounts to about 20% of my operating costs which putting it mildly, is hefty. I can accept no discounts (heck I was even launch customer and not one penny discount!) as in real life but leasing rates are very high. On the other hand yields are too! There has to be a balance, keeping in mind this is a game. In reality, major airlines do actually earn their money on LH and use regional jets as feeders (they loose money). Look at the fuel consumption of a CRJ and an A380! Problem is people insist of flying CRJs on 1000nm flights!
As i described before airlines also sell and lease back aircraft (such as B777 and A380s) which creates an other skill.
Lease costs, in my opinion, must reflect reality as the list prices actually do.
BTW, when returning a leased aircraft, planes are returned in the condition they are lease, therefore with the leased seating and 100%ish condition. This is good idea to keep airlines on their toes in MT6, maybe.