An always lit in vehicle display and DRLs that are just always on headlights makes people forget to turn their lights on when it's dark. This isn't a problem for them since they have their headlights on but drivers behind them don't see them from a distance at night because their tail lights are not lit up. This is particularly dangerous in traffic where everyone else has their lights on.
Making DRLs mandatory is tripping over a quarter to pick up a penny because it enables this behavior.
If everyone's car just did this automatically, the world would be a safer place. Why would you ever want the lights off?
Once LED lights are more standard and there's less issue of replacing bulbs or wasting electricity it seems a no brainer.
And finally, I think there was a Polish study that said that yeah, while with the lights on you are more likely to notice a car, you are less likely to notice a cyclist - and hitting the latter has much worse consequences than hitting the former. So it might have made things worse.
Most OEMs just make the headlights (and the headlights only, not the tail lights) always on in markets where DRLs are mandatory. The latter is what you get when you do what Canada did and require DRLs and don't require them to also be poor at being headlights.
Pretty much any time when you want to signal the intention of not going anywhere is a darn good time to have your headlights off. Cars actually have parking lights for exactly this reason. They also work great for creeping around your own driveway without throwing too much light on the windows of houses in the very early AM.
My last car rental, some moron previous renter turned the switch to DRL only instead of Auto. I did exactly as you described and drove with no tail lights and headlights that seemed dim but it wasn't my my car so it must just be that way. Eventually another driver flashed his brights from behind and I realized my mistake.