I agree the excursions do seem to be rushed and you don't get as much time as you would like in the various cities, however, ships like busses and trains are on a prebooked schedule which they have to adhere to, plus, to be honest, the whole point of cruising (IMO) is to visit as many places as possible, most cruise ships sail at night arriving at a new destination virtually every morning, if ships stayed in each port overnight it would have to spend the next day in that port too. a standard 7 day cruise would mean you would only get to visit about 3 different destinations, if you want to explore a particular city throughly then a 2 centre hotel holiday or city break would be a better option than a cruise.

Completely agree that cruise liners should stay longer in ports as you could then enjoy the nightlife or explore the cities a lot more. I guess cruise companies don't do this as whilst your on shore your not spending money with them in the bars etc and the port's docking fees comes into it?