Why they don't convert the A380 into big cargo planes?

A380 is no longer in production and airlines are beginning to get ride of them, some were already scrapped. Wound't it make an good giant freighter? Why not?

It's all about fuel efficiency. The older ones are less fuel efficient and the air lines tend to replace older craft with more fuel efficient. Even the freight carriers look to newer aircraft to deliver the goods

Too hard to load the plane because of the size, height of doors above ground, and one can't modify the passenger doors without heavily modifying the frame and a lot of the things like wiring, hydraulic lines. That would require recertifying the plane for service. And the freight hubs are not designed for that size airplane. Just too expensive.

Damn I did not know that

Converting to a freight hauler involves modifying the aircraft with sturdier floors and usually a big cargo door. It takes a lot of years of use to cover this expense. Airbus aircraft have always been considered "expendable". At the end of their service life as a passenger aircraft, they are near the end of their airworthiness. Most Boeing, McDonnell/Douglas, Lockheed, and Convair, aircraft, had a lot of hours of useful life left, making such mods economically feasible. Not so with Airbus.

1- that A380 is still in production. There still are 55 planes that were ordered and yet not delivered--although it is possible that some might get cancelled. At the current rate of delivery, it could remain in production for a couple more years. What changed is that Airbus ANNOUNCED that they would stop producing it.
2- no A380 has been scrapped yet, you are amazingly wrong
3- the A380 was originally proposed in two variants: passenger and cargo. The cargo got only a total of 27 orders by the time the first prototype flew, and those were all cancelled before the first delivery. Lack of interest means no cargo variant were ever delivered. If there was zero interest in new A380F, why would there be in a converted ones?
4- Boeing 747-8F, the cargo variant of the largest and most recent 747 model, has also sold about 10 units per year for the last decade (which is nevertheless twice as many as the passenger version of the 747-8). Apparently there's not that much demand for very large cargo plane in the first place.
5- Airlines operating the A380 are apparently satisfied with them and no necessarily in any rush to get rid of them.
6- if you are somehow thinking that removing the deck floor would open a huge cargo volume, that is where you are profoundly wrong. The floor of the A380 is part of the structure and contains many systems, pipes and ducts, and removing it would required extensive rework and strengthening of other components that would end up costing more than the value of the plane. For over-sized cargo, the conversions used so far is to replace the upper part of the fuselage with a large bubble, as in the Airbus Beluga XL. Given that Airbus is essentially using them for their own need (moving parts of airplane between factories) and that they envision a fleet of less than a dozen, there's apparently not that much of a demand for super large cargo plane anyway.

Air freight operators have been flying Boeing 747 freighters for years. No doubt that a few A380s WILL be converted to haul freight of some sort, but probably not for package haulers like FedEx or UPS. The big airplanes are typically used to haul specialized or oversized cargo that won't fit in a "normal" container.