They also do it because if on the second morning the seas get too rough then the tenders wouldnt be able to function and bring any passengers back on board who happened to stay the night in town for some reason. Kind of sucks you cant stay in Cabo until the wee hours though.
2008-Valor and Glory
2009-Spirit and Splendor
2010-Freedom of the Seas and Mariner of the Seas
2012-Allure of the Seas and Navigator of the Seas