The last Lockheed Starlifter was retired in 2006, but the Ilyushin “C-141ski” still flies on. Imitation truly is the sincerest form of flattery.
I’d have to say it’s due more to the number of hours flown. Our transport fleet is constantly flying. Russian transports fly a fraction of the hours ours do. I wouldn’t be surprised if the average number of hours on the C-17 fleet isn’t higher than the average number of hours on the IL-76 fleet.