Why don't Cell Phone have built-in Answering Machine

In the pre-smartphone era, I was extremely addicted to samsung's flip-upside cell Phone, they were tiny and had better lcd than any of their competitors. But above all, they have had built-in answering machine. Since I work late hours, so sometime, I won't get up early like 9am, so my customer would keep recording the message and I would respond to them as soon as I would be up.

I didn't have to dial any voicemail number etc, they were saved right in my box and I would delete all of them before sleeping.

Now in the era of smartphone where this sort of functionality is child's play. We have desktop level smartphone. So there are no hardware limitation, only limitation I can see is 'carriers' which would force OEMs to not offer it. Which is plain wrong for the consumers.

I have searched everywhere, I can't find any app for iOS or Android. Which is equivalent of carrier's voice mail. Samsung offered this some 10 years ago. why not today even samsung itself or any other OEM.