Losing your score when you die is a remnant of the original game direction. It was based around slot machines and game addiction. Thus, not being able to quit before losing meant losing it all. I decided to keep it since bills eat up your earnings.
The score is only saved if you quit on purpose before dying. Your highest score is saved in the local storage and you can see it on the title screen :)
Thanks for playing, and thank you for your feedback!