Those are some pretty pessimistic percentages there.If to win one of the bigger base reward prizes is 0.10% and 0.20% respectively I wonder what will be the percentage to hit Amazon Gift Card or the Rolex,I believe that to be in some 0.000x% percentage most probably but it maybe even lower.Luck is a big part of gambling also but those statistics keeps me like they say with foot on earth and not willing to expect big prizes from the WoF spins,normally before reading those details I always hoped in every single spin that some huge prize is going to fall but I know I am over optimistic when gambling.
The fact that when you increase the odds just a small thin hair line, then you are losing plenty of bitcoins as a casino. What you earn may not be a lot more, you might get like a small tiny amount more, but at the end of the day they will be losing this to tens of thousands of people and not just you, so even 1 satoshi difference is 10k satoshi per day, or if we are talking about 1k satoshi per day that is 100k lost per day, and when you hit that to 365 days you get yourself a ton of money lost per year.
I am not saying that what you are saying is not feasible, they would have to sit down and calculate how many more new people they can get and how much they would profit from it. But I feel like it may not work for them.