I’d guess the simple answer may be that people don’t care/know, but for those that have ditched Facebook for whatever reason, yet still use Instagram, it’s a little surprising.
Is it partly a result of it being a more focused/limited form of social media that filters out some of the stuff people didn’t like from Facebook?
Whatsapp doesn’t use a lot of battery at all for me.
For me it’s not a deal breaker. But in terms of standby it’s number 1. (Because I deleted everything else).
If I open BBS I get a mess of partial wakelocks: https://imgur.com/a/KzMQhR9