It's always the assholes that keep this shit spreading.
More irresponsible than driving a bus drunk for weeks.
It's easy to point at people doing this stuff and call them assholes, yes, but the way Chinese authorities have been handling this stuff also contributes to the psychology of why someone might do this. Instead of making it safe and secure for anyone who declares honestly, there have been many reports of how people declared that they've been to Wuhan and their information was leaked by authorities, they were ostracized by their communities entirely while on home quarantine, and so on. If there's a straightforward and non-judgemental form of handling this - like how it is in many countries now, most people would be comfortable to declare honestly to protect themselves and others. But when resources are stretched so much in China that even if you declare, you might be seen as a threat or burden, and you might not even get the treatment you need, that stress and anxiety can drive many people to want to avoid all the potential hassle.
If the example of drink driving, imagine a group of people going for drinks at night. After drinking they walk back to their cars, and there's an officer at the parking lot asking if anyone is drunk. If anyone admits they are drunk they get treated like a criminal and other people start throwing stones at him. Would it be unusual in this case for some people who feel they might be a little tipsy but don't want to be treated like that to declare they are not drunk and just get into their car and drive off? Yes it's irresponsible but as a society people should make declaring inconvenient things as easy as possible without added pressure.