Wdym why not? What’s the better tech? Scan whole body for login? Or something else? Vein ID? Palm ID? I know all iPhone had Touch ID at one point and it was fine until iPhone X came out with Face ID and here we are.
Better tech is whatever best fits the need of the users and how they use devices. Better tech is giving options to different users with different needs.
Some countries have upgraded their elections from voting machines to pencil and paper, because it is better tech. Better tech is not the newest or most impressive, it is whatever lets you best achieve a desired objective.
The strange thing is it seems most people who care about under-display TouchID are those who also say they would never use TouchID and how great FaceID is [for them]. Those of us for whom TouchID suits how we use our devices do not care where the sensor is.
I have an Android phone which has a sensor on the back. It is not glamorous, it means cases need a hole to access it, but it works. It is located in the area my finger will naturally be when holding it. Not the best design, but very good tech. Putting it on a button would be much better design, and still very good tech.
And as for security, can you still have the option of not using a passcode to unlock? But an iPhone is not an airgap device, it is always connected and used in public. Using one is a conscious decision to put some security at risk, better tech is not the most secure, it is that which best balances usability and security. And that again comes down to user choice.
Have it turned off by default, show a warning when enabling it that "Apple recommends FaceID as a more secure unlocking method," if they must. But it still offers a good enough level of protection that it is not unacceptable to use, that Apple still use it on various products.
For most ordinary users the biggest risk is the phone being grabbed rather than someone stealing their fingerprint so they can sneak into the office at night where the iPhone is left on a desk, hide under the desk when the security guard points a torch in their direction, before attaching a flash drive to download a set of documents that will take three minutes, during which the owner unexpectedly walks into the office before suddenly being called away again just as the download completes.
Other people like FaceID, they want more security, it works for them, it fits well with how they use their phone? Then good for them, nobody has said they should be denied any of that. It is very weird though that some of them are saying those for whom it does not work well, who do not need the extra security, that find it an inconvenience to use, should be denied the opportunity to use an iPhone they way that suits them. That is bad tech.