It is all about having the right gearing range for the conditions.

I ride quite a few 1 by x drives because I ride a good number of bicycles with internal gear hubs as well as a 1 by 8 mountain bike which can handle urban assaults and some pretty challenging trail conditions.

My primary commuters have a 1 by 7 internal gear hub and a dual drive which is a 1 by 7 (cassette) by 3 (internal hub) which gives me 21 speeds and some very decent gear range.