This is a limitation of Evernote for iOS. I’ve heard rumours that it will be changing soon — but who knows. If you know your tags, though, it’s still pretty easy to get around. Search helps as well. Evernote for iOS does keep a limited record of your searches, so you could put your most common tags through search on iOS and then head back there when you want quick access. This won’t be limited to just tags, however.