One can literally chose different reasons to lie inorder to cover up their loses but I don't find myself doing that knowing fully well I don't have any reasons to lie to a loved one. whenever i counter loses it seems to me as an opportunity to withdraw back from my activity, cause every loses is an opportunity to learn and restrategise.
It seems to me that lying about losing can only motivate us to lose very big, when money from savings was lost. But it will still be obvious if it is money from the family budget. If the spouses have separate budgets, then of course it will be easier to hide, but problems with gambling will be difficult to hide and it will be noticeable to loved ones. I believe that lying is the first step to ruining a relationship and breaking up a family, so before lying, you need to think about it very carefully.