I can’t remember the last time I drove with just sidelights on - probably back in the early 1990’s. Sidelights are often referred to these days as position lights or parking lights, suggesting they’re intended to be used primarily when the car is stationary- e.g. when parked up at night in a poorly lit location, when it might be creating a potential hazard to other road users. Turning on a car’s position / parking lights / sidelights (or whatever you want to call them) in these scenarios helps other road users to see it.
IMO, position lights / sidelights aren’t really bright enough for other road users to be able to see you clearly when a car’s being driven, especially in conditions where visibility is reduced, such as rain during daylight hours or very dark days. Also, in most modern cars with LED DRL’s, the DRL’s double up as position lights / sidelights but operate at a reduced intensity / brightness level compared to when they’re operating as DRL’s. So when a car is being driving with only sidelights on, the visibility of that car to oncoming road users and pedestrians is reduced, making it a potential hazard to others.
I always leave my lights in the ‘auto’ setting, but I’ll manually override the auto setting if I need my headlights on at other times and the car’s light sensor hasn’t switch the lights on automatically (e.g. daytime fog, daytime rain). Driving using just sidelights is a ‘no-no‘ for me - I don’t want to increase the risk of causing - or being involved in - an accident because I’ve reduced the visibility of my car to other road users and pedestrians.