Historically, ships that transport people have served as hotbeds for infectious diseases. Even troop transport ships were found to have been the disease highway for spreading the Spanish Flu of 1918. On ships, people from all over the globe tend to crowd together in theaters, pools, lines, and buffets where illness can spread at high rates. As long as cruise ships serve as a popular vacation option, the risk of contracting and spreading illness will remain high.
Since the onset of COVID, cruise companies have worked diligently to ensure that passenger safety is their top priority. Slow operations during the pandemic allowed cruises to focus their efforts on innovative solutions that guarantee passengers fun and excitement but also guarantee a safe journey. It's difficult to ensure health and safety without reducing freedom and enjoyment, but the cruise lines have excelled and as the world opened up so did more opportunities for vacationers.