My sister is really cautious and wear the bag across.
But they wait until the tube or a small pass on the sideway, when people have to come close together.
So you won't feel any touch on your bag.
As my sister went free again - she had only the stripe over her shoulder. They cut the bag with a razors knife or similar tool. zig zack
This will be in every big city - I don't name any minority here ... neither the former majority in some parts of east European countries ...