What's with (Native American) Indians and casinos?

I received with joy this news of the Mashpee-Wampanoag people receiving "federal recognition as a sovereign American Indian nation."

But I also heard that among the many things they wanted to get started on was building a casino. Now, while I have nothing for casinos and gambling, I really do not understand - why is that thought uppermost in their minds? Is that the only/best/most-lucrative way of making a living that the Indians can think of? Something inborn, some talent and predisposition to running such ventures...

People who themselves have been de-authenticated and touristified, why do they not try to disassociate themselves from further stereotyping?