system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we wear clothes/Are ashamed to be naked?

Even in cultures where women are topless, it seems the they still often wear shorts or thongs etc. In most cultures it's illegal to be naked. Why are humans embarrassed to be nude?
gpt
Clothing to mask sexual triggers is a social technology, which is nearly universal because it allows people to live together in groups and set aside (some of) our enormous sexual urges.  Most of the way that we interact with the people around us constitutes *technology* that was developed over millenia to enable ever-larger groups of people to get along (e.g. the development of priesthood classes, magistrates & judges, rule of law, etc. -- though those cliché highlights are only, well, cliché highlights of a long process).  Because people are even more sexual than bonobos, masking genitalia is a useful way to damp down (or sublimate, anyway) sexual desire and focus attention on other types of interaction.

Nudist groups in western society are actually a supporting example of that view -- nudist clubs and colonies, in general, adopt very strict taboos -- for example against anything vaguely construable as lewd in public spaces -- to enable clothes-free interaction. 

EDIT: Sorry, that was ELI15.  I'll try again...

When you're older, some changes will happen to your body.  Parts of your body will grow and change, and you'll start to grow hair between your legs.  You'll also start to feel, well, strange around girls or boys.  That is the way your body makes more people: your body really, really wants to turn you into a parent by getting you to help someone else make a baby.  That urge to help somebody else make a baby is so strong that it can keep people from helping each other in other ways.  When people settled down, thousands of years ago, to make villages and towns, they had to figure out how large groups of people could all get along with each other.  Wearing clothes is one of many things that help, because it helps people keep from thinking too much about making babies with each other.

There are some people who think that grownups should be able to work and play together even without any clothes.  Those people are comfortable not wearing clothes in public, and they even form clubs where people can go hiking or swimming, or just have picnics together, without worrying about clothes.  Those people have their own rules for how to act, so that they don't spend too much time thinking just about making babies.  Since you're five, your body doesn't give you those strange feelings yet.  The weather is great, and your friends are all splashing naked in the sprinkler outside.  So run along and go play with 'em!