Rationing in the UK went on until 1954, nine years after the war ended.

To me, another be part of it is that the British seem to have an awful penchant for giving delicious things names that sound like Victorian euphemisms for something awful. Spotted dick and toad in the hole sound like they would be ways for Victorians to talk about their STIs, and I'm unsure what exactly Gentleman's Relish would mean, but it strikes me as some sort of medieval form of punishment on the peasants.

That's how traditions are born.

folks had to keep eating like the Luftwaffe was still blitzing London

To be more precise, they had to keep eating like the Kriegsmarine's U-bootwaffe was still sinking the ships with the food.