They are confident, they are underestimating the virus.
They are underestimating the virus though but some people still going outside to do an errands to sustain their needs. No one is safe actually until the vaccine release globally. Once vaccine is out people can go to the casino but these days government allowed businesses to open. Must follow the precaution to be safe from this pandemic era.
We can't blame them though. People thought that they are strong enough to fight the virus since the recoveries worldwide is around half of the total cases and the mortality rate is low that is why they are underestimating it. I can't blame those people too who really wants to go outside because of boredom and some errands like you said.
Until there is no vaccine, there is no safetiness of the people is low unless you have a good immune system then you can fight the virus with yourself. Even though the vaccine is out, I doubt that gamblers will go to the casino immediately. They will wait for weeks to months I think before they will return or they will just gamble online.
Firstly, if the reopening of stores, casino and business is not very important the government wont have allow it, remember Las Vegas Mayor (Carolyn Goodman) once ask for the reopening of casino because the quarantine wasnt completely the solution but she was rebuked by people and by the Nevada leaders.
Second, this is not the act of underestimated the virus but saving ourself from something that could give than the virus itself.