That's exactly what the Gmail app does too. What other features does it offer that the Mail app doesn't? If none, then why does it need to be so huge?

I picked on Gmail because it's the most recent culprit that I have noticed creeping (sometimes jumping) up in app size but it isn't the only one guilty of this. Like I said in my original comment, the Reddit app is 13MB and does a bit more than the Gmail app. I can read/write posts and comments and view images; similar features to Gmail, but I can also watch gifs and videos. Can someone explain why there is an order of magnitude of discrepancy between the two apps sizes?