Even if you have no trouble remembering a seven digit code, there's nothing to stop a malicious actor who determines that code from entering your apartment. At

Even if you have no trouble remembering a seven digit code, there's nothing to stop a malicious actor who determines that code from entering your apartment. At least with physical keys you have absolute control over who has those keys, and don't have to worry about somebody spying on you as you're punching in the code. The fact that it takes two seven-digit codes to enter your apartment (one for the lobby door, one for your apartment) only makes cracking the code more difficult; it doesn't change the basic problem that control over entering the building (and your apartment) is freely available to anyone who determines the code.