Genuinely curious if this could ever be a possibility one way or the other. Feel like it would be very popular. But it will probably never happen

Maybe it could happen if the casinos are charity homes but they are not, so therefore, it will never happen, because they are just like every other business venture which needs to stay in profits to continue running the daily affairs of the business. A zero house edge makes them vulnerable and that includes a 100% RTP too. So OP, stop dreaming and face the reality.
Absolutely, casinos will never do that, their major aim is to make profit from gamblers and not to act as a charity home. Besides they are just like every conventional business owner whose aims is centered on profits, the only reason we see them running some incentives programs and bonuses is to stand a better chance of attracting gamblers in the competitive market. And just like Hispo said they'll only make RPT 100% during their Ads to get those bettors who fall for easy tricks. Even the bonuses they give to bettors, they wish you loss it all back to the system.
Also, some gamblers seems to be confused about the impact one hundred percent of RTP could have on their personal sessions on the casino or what the significance of zero edge would be for gamblers in general.
Even if those conditions were met by some casino, still it would not mean all gamblers would be profitable. It would only mean the casinos would not take money from gamblers, but gamblers how are lucky would continue to get money from gamblers who are unlucky, the casino would function just as an escrow holding the money and they would not profit from the volume of money going through their casino games and bookie.
Still it could be easy for some novice gambler to get confident and then reckless, all ending up with the loss of their bankroll.
So even if the casinos do not get any money from gamblers, gamblers would continue to battle to get money from one another.