Retina apps are too big
Retina displays are great. Everything looks life-like. But there is one big compromise...
Browsing the web, enjoying your photo collection and etc on a Retina display only bring benefits. There is no compromise here.
But when it comes to using third-party apps and stuff, those optimized for Retina display take up enormous amount of storage. To make matters worse, many apps accumulate more and more data as you use them. For example, Facebook app on my iPad takes up an astounding 174MB, of which only 30.1MB is the size of the app. The real problem is for games: graphics-intensive games optimized for iPad's Retina display easily take up more than 1GB. The selling point of iPad is the variety and choice of iPad apps so this is kinda unacceptable. What's more, games optimized for Retina display do not necessarily look better. They are just marginally sharper and thus cleaner, which do not necessarily make gameplay significantly engaging or fun.
Of course, one may say Apple has no reason to somehow introduce new technologies to reduce the file sizes because they want customers to buy more costly devices with more storage. Hmm then why did Apple introduce Fusion Drive when customers could only buy the much more expensive SSD for faster performance? So I think one of the software innovations Apple can do in future is some new file compression technology or sth to minimize the size of Retina-optimized apps and also the accumulation of data after they are downloaded and installed. Agree?