it would really be just that depending on what work you do have but in overall or frankly saying that its never been good to play or whatever things that you would be doing in working hours.
You arent that getting paid for making up those activities but rather you are paid on doing with your job, you could do the rest when you do get home.
You know, many of us, forum members, read and post on the forum during their working hours. Many use work PC to read news, some watch YouTube parallel working. Some might take a pause (without asking others) and out for 5-15minutes for a smoke. Other might have a stomach problems and run to WC every few hours. If we have a working days from 9 to 5, it does not mean that we starting working at 9, and finish at 5, and between those hours we only work-work-work-work. Frankly, we slack a lot during working hours. So where is that gap between reading news at work (meaning not work) and gambling for the same 5-15min (meaning not working)? Why it is not good to gamble, but to got out and smoke every hours and with every colleague is ok?
But if this is not the case then you could get in trouble, as even if taking a small break here and there is also not something anyone will make a fuss about it, if you are often caught gambling or watching some youtube videos you could get fired, or at least you could get on the short list of those that have the power to take that decision.