Do you think it is necessary to give tips or it is just a tradition that is required?
Its not actually necessary but rather it would really be just depending on someone whether he would be giving out some tips on the time he would win jackpot or something big.
~snip~
^Definitely right, it is not necessary and not your obligation to tip them.
But a tradition of giving tips especially when you have hit the jackpot is not new in gambling. As mentioned on the first page, Rollbit.com has this function by sending tips, though I did not try it yet because I did not send tips but this feature is available on Rollbit.com. If you feel to give any small amount in return f their good service, that is not a problem either.