This is the norm on Android, and means you have to have huge scale before it's worth releasing a paid or subscription app on Android, which might be viable at much smaller scale on iOS. It's part of why Android's ecosystem has so much prominent adware. Common wisdom (backed up by data) in the industry is that, generally speaking, your "conversion rate" for paid or subscription apps on Android will be a tiny sliver of what it is on iOS, unless your app is very unusual.

There are a bunch of factors that probably cause this, but they're all mixed up and intertwined so it's hard to point at one and go "that's it, that's the reason". Selection bias of the user base (think: socio-economic status, and maybe even average technical know-how or comfort with software); iOS users use their devices way more than Android users, for all purposes (but, is that because of the previous thing? Maybe); it could have something to do with the ecosystems the two app stores have cultivated, causing different levels of trust among the two user bases when it comes time to spend money; it could have something to do with the quality of the experience of using the respective operating systems themselves.

Probably all of those contribute some amount. It's hard to say, though.