The apparent discrepancy is probably due to the relative size of whales. According to the FBI, though SP was recently recorded as winning or losing up to 100K during a gambling session (maybe even more in a past rarer “mega session”

. His average win / loss was probably 20-30K.
This made SP a comped “small whale” in the gambling universe hierarchy. A comped small whale can be a star at one level of casino, but also be comped though far less noticeably at another level of casino such as the ubber upscale Mandalay Bay where whales may swim in pods.
Then factor in relativity in perception. SP’s siblings seem to have more limited incomes. Thus, SP receiving a certain level of attention and a certain level of cool comps from well dressed casino managers, acknowledgment as being “the Man” from waitresses, and SP’s ability to “call the shots” at a casino may have been seen as impressive relative to family income and doubly so given an apparent pre-disposition to admire alpha male shot callers, it was also relative amongst “whales”.
If there was a decline, it was slow. Another poster cited an FBI reference that SP was not in debt and always repaid his “markers” (casinoese for personal credit IOUs) promptly.
Casinos place a lot of emphasis on long term averages for all their customers when managing risk. Nearly all gamblers lose in the long term (some far faster than others). Then factor in that banning customers for superior play is bad for business as word gets out.
As a result, some casinos may decide to “eat” losses from the occasional smart video poker / slots guru who after years of mind numbing play, has learned enough of the changing software algorithims to gain say, a 1.0% advantage if he is playing perfectly and if he is on a machine he knows. It is better just to change machines- but not too often as this is considered "unfair" by the "pros" and word gets out, or upload new algorithms during maintenance periods.
As a side note, I read a sad account of a former surgical nurse (intelligent) turned video slots addict. Like SP, she spent years on the machines. Eventually , she was able to gain a small advantage over the casinos if she knew the machine, if she played perfectly etc. Anyways, the casinos tolerated her winnings (if helped that she did not have the cash flow to really win big), and only banned her when she and a boy friend started offering classes to other zombies that were too well informed for casino comfort.