Tread will help with grip in snow and ice, in mud, or or on wet grass, but on a surface like concrete or stone it really comes down to material characteristics and surface area. Quality road bicycle tyres are often slick, but can be ridden in wet conditions. Some have a fine tread, but this is basically marketing, to allay the fears of those who don't 'trust' slick tyres. The tread doesn't improve the grip and I would rather ride on slicks as the tread detracts from the ride quality. Rock climbing shoes which test the grip of footwear to the limit have smooth soles.
The main argument for Topys as far as I'm concerned is wear. I agree that leather soles can wear well when worn on concrete, even in the wet. I've had some that have lasted a year with almost daily wear, walking 10km+ a day. We don't always have the option of walking on a surface as kind to your shoes as smooth concrete. Around my way the predominant paving material is rough asphalt, often eroded over decades, exposing the sharp stones in it. It's like walking on a cheese grater, and can destroy leather soles in short order. For this reason for shoes for day to day use I choose rubber soles where available. If rubber soles are not available, then I am looking at accepting disgrace and putting Topys on leather soles. It would be nice to wear leather soles, but they are not practical in this environment.
DWFII, you mentioned earlier that Topys can be worn past the point of no return. Is this continuing to wear them after a hole or soft spot is first apparent, or does it happen before this? If earlier, how would you tell, please?