I know what David means, and am sure that he does not expect any cruise itinerary, no matter how well planned, to provide an in-depth experience in countries visited. Rather, a cruise can only be a "sampler" of these countries.
Problem is, port time on some lines' iteneraries is so short that it does not even provide a good sampler. Then, when you subtract from the scheduled port times the time wasted in lines to disembark and embark again (especially on the larger ships and/or at tendered ports), the passenger all too often gets left with very little true port time.
Some lines may do this, beacuse they perceive that is what customers want. I can recall our first cruise selection process 16 years ago. As first-timers then, we selected the sailing that visited the largest number of ports in a week, period. We didn't consider how much time was spent in each port, and we didn't consider the time wasted in lines -- as we did not know about them. I'll bet many first-time cruisers do the same, and that lines that market to a lot of first-timers intentionally put as many ports on the schedule as possible.