Well for college kids and young people you need to know if an event is being created or you're being invited somewhere. I don't want to check my phone every 30 minute throughout the day and nobody around me is rigid enough to plan everything days in advance. Sometimes you wanna go on an impromptu road trip or to a party or maybe there's a test you didn't know about and the study group is organizing a session. Maybe you just wanna be a part of the conversion when you're friend group starts taking instead of always pitching in hours later.

Typing this all out, these are all young people things so i don't expect someone with kids and a mortgage to have the same experience but imagine if your sms app was littered with ads and you couldn't turn off their notifications without missing messages from your children needing assistance. That's basically the type of dirty attention capture these companies are engaging in.

If you don't understand why someone would use snapchat or other image based social messaging apps then you won't understand this particular issue as you don't have it.