Why? 🤷🏻♂️
As long as the train is almost empty, I see no need to sit like a granny holding her handbag on her knees. With my scoliosis I also prefer the centre aisle. My bag is always clean. Why place it on a sticky ground?
If more people enter the train, of course I immediately free the space for the next pessenger or even invite people to take a seat.