Even when the webapp is great? I don't see why they or anyone else should maintain several versions of the same app, focusing on one version and iterating quickly is surly to everyone's benefit.
I wouldn't describe the webapp as great. Since it attempts to emulate aspects of UIKit it suffers greatly from the uncanny valley effect. The performance and feel is poor compared to a native app.
I realise it's more convenient for Google, but I struggle to believe that's the primary concern when a company of their size develops an app for a platform with hundreds of millions of users.
To me it feels the app is intentionally crippled for some business reason. Perhaps it would be more difficut to target ads in a native app, or maybe they want to push people towards Android. As a user, I really don't care and it reflects poorly on them to produce a substandard experience for their users.
Some desktop app developers don't see why they should maintain several versions of their app, put out a single Java GUI across platforms, and get shunned for it. (Granted, web look and feel on mobile likely won't be that bad).
I think this issue boils down to perceived ROI on development costs (and 'push web technologies' agenda in Google's case) rather than quality.
The web app is fine, but there's definitely room for improvement in a native app. This thing offers me nothing that I can't get by using the web app for most stuff, and using Mail.app for notifications. Which is what I've been doing for a year, and will continue to do.
