There are a lot of people who live alone, or eat alone. Not everyone is living in a family. 1 in 5 never marry, almost half divorce, some are widow(er)s, plenty are single(ish) and living out of home, some are devoted to their careers or other causes. Even if they do live with others, they may eat separately for various reasons. This is not the case for a lot of the global village's demographics, but in some areas it is very much the case. This idea is formed from a niche market that is created by these realities.
Bread is a perishable food product. It gets mouldy. Old bread is a problem for those who eat it, but not in large enough amounts to finish a loaf before it goes mouldy. It is a dreadful waste, costly to the producer, the consumer and the planet in general, as it rarely makes it to a compost bin (accommodation for single people rarely has the facilities for composting, especially in cities), and is bad for bird's intestines if fed to them.
Bakers have an opportunities here for a new product. If they baked half loaves, there would be a lot of people who would buy the product for said reasons. Also, a lot of people who hesitate in front of the bread thinking "Yes, that's easy and quick, oh, hang on, the last three times I bought bread half of it just went off, no, I won't buy it, I'll by a couple of buns, cans of stuff and biscuits instead, at least that won't be wasted." will change their minds. Freezing half the loaf is not always an option as it takes up valuable freezer space (they often freeze meals for convenience), if there is a freezer. If they do freeze the bread, it is a nuisance in thawing, losing quality, taking time. If it just gets too hard, people don't bother. Also, as a baker, you could add a higher price for two halves, thereby further increasing profits as well as reducing waste. Also, the bread will be remembered as relatively fresh by the consumer, inducing nearly subconscious re-purchasing. Also, bakeries and supermarkets would benefit by more frequent visits by the customer, increasing impulse buys.
Well, that is just an idea, but I think it could work, increasing the sales of the bakery, pleasing the customers, and help the planet reduce landfill and greenhouse gases. Also, it is a good idea for novelty breads and market experimentation.