Welcome to FT. But I don't think your feedback is accurate. After the TPE crash, I recall when they started rolling out new J on the 77W many years later, I was able to enjoy almost gate-to-gate entertainment. But yes, they discontinued the practice about a year after.

The practice of not allowing headsets isn't just restricted to SQ. CX prohibits it too, but NZ and QR allow it.

Another irritating cabin rule - the FAs typically ask everyone in Y to straighten their seats like 20-30 mins before touch down. I understand the need to not have a reclining seat obstruct the passenger seated immediately behind during an emergency, but FAs insist this on the persons seated at the last row too. I once asked what the rationale was and the FA replied - to be fair to all passengers, everyone must do it!