Ask the bees what the point is and why they do it every year.
Regardless, it's been
demonstrated that a small portion of the bees living in the hive in August are still alive at the end of December, these being obviously 'winter' bees. In this particular investigation, every bee in the hive was marked a certain colour, with colours being changed at a 12 day interval. The results clearly show a number of bees (marked blue in this case) who were in the hive in August (when all unmarked bees were marked blue) and who were still alive and kicking at the end of December.
As I said previously, these bees don't form the bulk of the winter bees but demonstrate the
onset of winter-bee rearing.
These diutinus bees don't need to sit around doing nothing till Christmas, even in Essex. Nor do they need to flog themselves to death. They are physiologically built to develop more slowly, so spending most of that period as house bees.
The full explanation is on the page I've linked above with further research described in the references. If you check
reference 10 , the authors conclude that
"During the development of the winter bee population, there is a period during which emerging bees can become short- or long-lived individuals in all colonies. At present, we know little about how this is determined. Differences in larval care may affect whether a bee is long- or short-lived; newly emerged bees that overwinter have significantly greater dry weight, protein, fat, triglycerides, glycogen and glucose content than bees that do not survive to winter."
In other words, they don't yet know
why but they do know it categorically happens.