Why does it seem that those 15 to 18 are in so in need of a boyfriend or girlfriend?

I read posts often from guys or girls that are 15 to 18 years old and many of them express the intense need to have a boyfriend or girlfriend. Some feel absolutely hopeless about finding a SO. Why is there such pressure at that age to have someone? I remember when i was in high school..i mean some had boyfriends or girlfriends but i didn't get the sense that there was a lot of pressure to have a boyfriend. maybe a guy to hang out with but not a 'relationship' Why do guys and or girls feel this way at this age? Why do they feel like there's a time limit. like if i don't find one now i never will. Don't they know that it can be easier to find a SO after 20 when teenagers turn into young adults.