Depends on how you like to tour. Personally I find bike touring to be more enjoyable when I keep the weight to a minimum. Therefore space has never been an issue since my camping tour load all fits inside two rear panniers and a small handlebar bag. If I needed more space there's lots of room on top of the rear rack and I could easily add a front rack. So my sport-touring road bike has all the carrying capacity I need with room to spare.

OTOH, more carrying capacity makes lots of sense for shorter utility trips that are generally on pretty flat terrain. In that case the extra weight isn't that important and reducing the number of trips is a big plus.