Cuz there is a BIG difference between dating and hanging out.
This has been the case as long as 'relationships' have been common before marriage.
Back in my parents day, which was a LONG time ago, bf/gf just meant going on the odd date, and more often they just went out on 'dates' and nothing happened. They did not have the deep emotional intimacy you think of as part of a relationship. That has never existed without sex, or the expectation of imminent marriage and sex.
Not to say some people haven't done it, but they've either struggled or been asexual.
You're supposed to want to have sex with people you're attracted to, and you're really supposed to want to have sex with someone you care about and are connected to and attracted to who is attracted to you. If you're not finding it hard not to have sex, something is really broken in the relationship.
If you are under 18 I don't think it has to mean sex. My favorite dates when I was 16-17 were just cuddling with a movie together. It's just other kids want gossip. I wouldn't get overly concerned. And enjoy whatever your relationship is.
Sex has always been an important part of relationships, its just that in some cultures in the years past you were supposed to marry first. Of course, people were marrying at 15. Then humping like bunnies. So really nothing has changed.