Where are all the young people living??

So I’ve been looking for a WG room for ages now and I’ve been wondering this whole time: where are all the 18 and 19 year olds living? I feel like all WGs on wg-zimmer.ch, comparis, etc. are by people aged like 23 to 28, I’ve rarely seen 20s and I think I’ve seen like one 19 yr old and no 18s. Where are they all??