I can't imagine myself "playing for fun". In my opinion, the pleasures in the game are very clearly associated with winning. And if there are no wins, for me, continuing to play becomes a problem. And even a series of losses makes or would make me think about continuing to play. I can only repeat that I do not get pleasure from losses. But if you play just for fun, then losses are just part of your game. Most likely, even a long series of losses will not be considered a "streak of bad luck". The same thing happens when you play for research purposes. Since your losses are small and controllable in amount, there is no point in doing anything special after a long series of "failures".
The average gambler would say the same thing, even if they play for fun. Only winning will make gamblers happy, even though sometimes the game atmosphere can also be entertaining. Gambling for fun is a way to be responsible about gambling, but most of us feel good when we win. Losing is certainly unpleasant, but because you are aware of the consequences of gambling, losing doesn't have to ruin everything.
Stopping after a losing streak certainly has to be done. I will not continue playing during a losing streak, it will only increase the number of losses I lose that day. Taking a break and coming back in a few hours is an option, but it's better to come back on a different day.