I'm gonna say overly high expectations probably have an effect here. As you said, these things aren't necessary for a startup with a small amount of users, but.

I'm gonna say overly high expectations probably have an effect here. As you said, these things aren't necessary for a startup with a small amount of users, but... very few startups seem to realise that, or consider that they won't become the next Google or Facebook overnight. So services like OVH aren't as popular as AWS because startups always buy on the assumption they'll suddenly hit it big, even if their needs are more modest. It could also come down to branding too; AWS and Google Cloud and Azure have done a lot of marketing in order to get themselves out there in front of the startup crowd, with whole conferences and events on how to use them. Hence some people are likely using them because it's 'the thing startups do'.