People store bread in the microwave to keep it fresh and keep it from going stale.
The bread is stored in the microwave like you would a bread box and the microwave keeps the air out of the bread and doesn't fluctuate the humidity and temperature which keeps the bread from becoming stale.
When the microwave is not in use you can simply use the microwave as a bread box and your bread will last longer and keep fresher.
A microwave does a good job of replicating the bread box, keeping air out and maintaining a constant temperature and humidity level.
If you have soft, enriched bread like challah, brioche, or pain de mie, and you know you're going to eat it within two to three days, then plastic is your best bet.
If it's going to take longer than that, then you should freeze it (also in plastic).
Wrapping bread in foil works, too, as it is airtight.
The invention of sliced bread in 1928 ensured the need for specific packaging to keep bread fresh for as long as possible.
Moisture-proof waxed wrappers provided the best solution before plastic wrappers were introduced.
Commercial bakeries use two types of ingredients to slow spoilage of bread which include the use of emulsifiers and enzymes.
Emulsifiers keep bread from going stale by preventing oil and water from separating.