Viewing gambling as a hobby can prevent us from being trapped by regret when we fail. Mistakes in making gambling a hobby can result in a high level of addiction that is difficult to control.
If you can make gambling a hobby, then whatever the results are, it will only be for fun, not for chasing victory. If you lose, keep chasing until you forget everything.
For me, it's like that in understanding that gambling is a hobby.
I don't think it really matters whether you worry about the lose or not, as far as you like doing it, it is your hobby. Going by the general definition of hobby and as stated by Op, it's anything you enjoy doing during your spare time. Of course, gambling can be seen as ones hobby but it's a dangerous one that needs to be approached responsibly. Hobby are meant to give us happiness whenever doing it but in the case of gambling, that happiness will not longer be there when you allow yourself to get addicted and battling with the loses. Regardless of joy one derive from gambling, it has to be done moderately due to it nature of how easily it can be addictive.
We must then ask ourselves where the line is, so we can try not to cross and turn our hobby into an addiction.
Lol, these examples you mentioned are hobbies of course but they are very shameful ones that we can not be proud to mention them as our hobby when asked in public. No doubt about it, most of the time these hobbies eventually turn into addiction but we are not ready for this argument since majority don't even know their hobby.