I'm sure an automated system can be built that is safe enough - the Elizabeth Line demonstrates that. But the reality is that upgrades cost a lot of money, and nobody wants to spend that money. That is what it boils down to.

With respect to attendants, they're mostly there on the busiest times at the busiest stations. Most of the time most platforms are largely unattended, and the driver is the only person present to take action unless you want to wait for the train to alert station staff to a situation that requires intervention.

If the solution to automate is to put in place attendants permanently on every platform I'm not convinced it'd serve much purpose.

With respect to the DLR, it's less than a year since the last time someone was killed by falling onto the tracks. While the DLR overall has a great safety record, it's far less crowded than several of the other lines. I don't think you'll get anyone willing to sign off on overriding the regulator there, given people have called for safety upgrades of the DLR too despite the few fatal accidents.