They're a perfect example of why the old adage of "do one thing and do it well" often doesn't scale as a business.

If platforms can provide a competing service, bundled within their package, many will pick it, even if it is worse quality. Dropbox had to expand (like Proton are - they started with email, then added calendar, Drive for file storage, Docs for collaborative editing, Pass for password manager, etc. Even if I would prefer they spend more time to fix gaps in their Android email app, I completely understand why they have to expand their stack).