system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What's the difference between one day (single use) contact lenses and regular lenses?

What makes the single uses lenses single use. Why can they not be used multiple times like other contact lenses?
gpt
One day lenses are much thinner and less durable, however since you wear a new pair every day they're usually more sanitary, can't develop buildup that can scratch your eyes, and generally easier for the wearer. 

Biweeklys and monthlys are much sturdier, but degrade over the lifespan of the lens. They also require a lot more care than daylies. You're supposed to rinse them for 5 seconds on each side with solution and let them sit in the contact solution for 8 hours, which can be a lot of work. Most people I've heard don't rinse their contacts, just soak them. 

Also, everyone's eyes work differently - some people can use the biweeklys for over a month, while other people's contacts degrade quicker. This can lead to either just living with worse eyesight or quicker replacement. Wearing contacts longer than their recommended use period can cause microscratches on the cornea from tiny amounts of buildup. It can be done, of course, but it isn't great for the eye.