I understand why it looks like this but in fact, Tom’s said on several occasions that Monzo is for anyone who ‘lives their life’ on their smartphone.
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The content that Monzo produces (i.e. their Instagram stories) is obviously influenced by the fact that it’s a relatively young team & Monzo seemingly doesn’t want to be perceived as a boring, distant bank.
But their tone is very similar to Innocent’s & Slack’s which, as a business productivity tool, obviously isn’t just aimed at millennials. It’s just more approachable.
It might be unconventional for a bank (& most companies) at the moment but considering how much more effective this tone is on social media, I can’t see why this won’t become the norm. So I expect people will get used to this. There’s no reason why a company’s employees shouldn’t be able to have fun while also doing serious work.