Most of Germany's leading aces cut their teeth in the Bf-109 so it's understandable that they would be reluctant to stop flying a plane that was still deadly effective in their capable hands and one whose abilities and limitations they were quite intimate with. Trading up to a Me-262 was an entirely different experience though, that being a revolutionary step up as opposed to an evolutionary one.

Interestingly enough Japan also 'catered' to its aces, many of whom were also extremely reluctant to give up the Zero even though it, unlike the Bf-109 which remained relatively effective throughout the war, became seriously outclassed by the Hellcat & Corsair less than two years after Pearl Harbor. It wasn't until planes like the N1K1-J Shiden ('George') and Ki-84 Hayate ('Frank') were forced on Japan's pilots that they began to accept the fact that these new planes were far more effective at holding their own against America's fighters than their beloved Zero and Hayabusa (Ki-43).

The Bf-109 may have been loved by the Luftwaffe's top aces but it's a safe bet that the main reason why it was manufactured until the end of the war was because it was cheaper, required less materials to construct and was probably easier to manufacture than the more modern FW-190.