It's worth noting whatever's left is often still not enough to survive the winter. They often replace it with a form of sugar water that doesn't give the bees what they need
From a study looking at the harms of this replacement:
However, the amount
of HMF that can be found in homemade syrups, which increases with temperature and acidity, can be much higher
and can cause significant bee mortality. Moreover, we highlighted the detrimental effect of syrups acidity on
honeybee survival, suggesting that the addition of lemon or any other acidifying substance to invert the sucrose
could be harmful and not necessary.
https://link.springer.com/content/pdf/10.1007/s13592-020-00745-6.pdf
From a less scientific source but talking about practices more broadly:
To harvest the honey, beekeepers either smoke the bees to subdue them, or trap them with a clearing board over one or two days. Others kill the colony altogether.
Oftentimes, beekeepers replace the honey they remove with a sugar water substitute. This practice prompts honeybees to overwork themselves to replace the missing honey. Meanwhile, the sugar water lacks the nutrients, fats, and vitamins that bees need to be healthy.
https://plantbasednews.org/culture/ethics/is-honey-vegan-the-not-so-sweet-truth/