Similar thing drives me nuts in GMail for iPad. Every time I open a link, it asks me to download chrome. I say no thanks, and uncheck the default “remind me later” option, yet few weeks later it happens again.
This is infuriating, and was one thing that motivated me to quit Gmail. I'm much happier now – traditional mail clients like iOS's Mail app work much better with a mail host that implements IMAP properly.
YouTube for iOS does something similar when clicking a hyperlink; it'll give you a popup for what browser, Safari or Chrome, even if Chrome isn't installed.
Been going on for a year now.