Why are premade teams allowed to be matched with a group of strangers?

I just got matched with 4 strangers vs a team of 4 premades and one questioning member.The questioning member was top but it didn’t matter at all because our top fed them.We could have had better communication too but everyone ignored everyone,I told them “please do not go anywhere solo and if you see someone go back because 4 others will appear.”We surrendered at 20 minutes I think.I was just trying to practice Irelia.Even my enemy laner got fed like 7-8/0.Why is this allowed?Why is a premade team who talks on call as well,allowed to go vs a team of strangers?