however many people enjoy it while losing .
I don't think I've ever seen someone actually enjoy losing - there are people who are less upset by it - but actually enjoying losing is a different story.
If you're gambling you're basically paying for entertainment..... You shouldn't expect anything back(as saying goes, hope for the best, expect the worst), but if you do, congratulations.
In the select scenario where you're doing it purely for the profit - then you should definitely expect to make a profit otherwise you'd need to go back and reconsider your strategy. For example, in poker if you're already making steady earnings from smaller stakes tables and moved up to higher stakes and you start losing/earning less you'd definitely want to reconsider.