I think there's a good case for a sloping TT on a touring bike because you want a high stack. Surly extend the HT above the TT junction just to contrive a horizontal TT but this is putting aesthetics above engineering. Which is fine I guess. I mean we all do that.
The other end of it is to have more seatpost stickout for standover as you say. More seatpost is also supposed to give you kind of suspension and make the bike more comfortable. Also desirable on a tourer.

I used a 4° TT on my Euro style trekking/touring bike and I reckon it looks nice. Only slightly sloping. Aesthetically I don't like the look of excessive seatpost stickout even if it is supposed to add comfort.