Returning to gambling isn't the main problem, but returning with the same mentality as before.
Exactly my point, most people gamble with the mindset of making it their major source of income and that is what makes it more of a bad habit. It is best known to people with experience about the effect of gambling so returning to the same bad habit would be the biggest mistake anybody would make.
With their return, there is always a financial constraint that would make them come back to the same habit again and can only be eradicated by self control and self determination.