Ever since the invasion of the Lucidians, a lot of people were gravely depressed at what happened and they've started looking for other ways to alleviate that feeling. It's an understatement to say that the evacuation centers all throughout the world are as boring as they go and that added to the stress and gloominess of the collective population.
That's why, when the invasion was finally over and repairs have taken place, a lot of people found themselves outside their houses, waiting for their insurance to give a heads up and cover the damages caused by the sudden invasion. Long story short, there were a lot of homeless people that day and they were given temporary dwellings on hotels that didn't crumble during the invasion. Needless to say as well, a lot of people had a lot of free time and so amusements parks and recreational locations are packed to the brim with people.
Man, I miss going to the amusement parks heuheu. o_o