Jeremy and Dena gave nice summaries from legal and management perspectives. Dena's experiences match my own in retail years ago, and I suspect the millenials aren't as practiced at cash handling, paperwork, and in many cases, math, as boomers were.
I rack up major frequent flyer miles with >80,000 actual-butt-in-seat miles plus running almost all bills through the airline credit card. To the point where I get about 8 free round trips each year and I use them for family and friends (and, yes, I love you guys, but you're not THAT good of friends).
But a point I haven't seen covered: privacy. Our recent thread on a tradegy of a young man perishing in the Bob Marshall Wilderness linked to news stories which describe law enforcement subpoenaing credit purchases down to the level of what beer was purchased. There was a tragic (and more pathological) case up here some years back when Safeway Club Card records were subpoenaed to show that the mother whose house burned down (with an accelerant) and who had recently purchased life insurance on her kids, also purchased a gasoline can at Safeway immediatley prior to the fire. (one kid died, the other jumped from a window and lived). In my life, I sometimes buy hundreds of pounds of fertilizer to kick-start the biological activity at a toxic waste site. Post-First-WTC-attack, I sometimes use cash so as to leave less of a paper trail.
My complaint against GoLite and a reason they've lost several sales to me, is that they don't ship USPS, only UPS. Their choice, sure. But I gotta think USPS comes to their business every day like it does to mine so maybe they just can't be bothered or got a better rate from UPS by promising 100% of their business. But $37 second-day-air (there's no UPS surface to Alaska) instead of $14 USPS Priority on $100 of stuff loses the sale in my case. Sierra Trading Post is more flexible and last I looked at my account, I've dropped about $12,000 on them over the last 15 years.
In the airline industry, Alaska and Southwest almost always make a profit, in part by making some hard-and-fast decisions - you WILL book on-line (essentially), all planes fly full, only one plane type (737), etc. Nordstrom's, REI and LL Bean take the reverse approach - largely, the customer is always right.