Nope, in my view gambling is a style of life rather than a hobby. True and abstracted gamblers will bet on everything even on tomorrow's whether and it doesn't matter with whom and where. They are gambling in the sake of process which is part of their psychologic life. I'm not in their class. For me personally gambling is a kinf of "hash-time" session when spending my leisure time.
Somehow someone considers gambling as a lifestyle or as a hobby, but gambling will indeed be a place to relieve stress when used appropriately and what exactly is the end goal.
As for how gambling is used as a hobby, it may start from games or bets that are just to release stress.
I myself do a few games just to fill my free time, and don't really take gambling seriously.
Gambling as a hobby or not depends on how their initial goal is, if it is indeed a hobby then there will be no pressure to always have to win or get profits.
But if gambling aims to earn more income, it will be a different story and there will be more pressure going on.