There’s a massive cultural thing in the US about the iPhone being the preferred phone and if you don’t have one it must be because you’re too poor to afford one. Obviously this is a result of marketing and isn’t universal but it is a surprisingly widely held view.
Given that, showing up in a group chat as a lone blue bubble marks you out as the inferior group member (in some people’s eyes). It doesn’t matter so much 1:1 but if there are 10 people the odd one out stands out.