I never thought that bookies could lose. as I know my own experience when playing both gambling online gambling and offline gambling, I more often lose than win. and I don't think it just happened to me, even though there are people who win a lot from gambling on the other hand there are definitely people who lose a lot too. I think the bookies of the possibility of losing globally is very small.
but what OP is mentioning are about Fair Environment meaning the house gives higher chance of wining from the players than loosing.
though this is very few(actually i think i have not experienced playing in one)i believe that they can survive by adjusting the winning chances.
There is fixed house edge, even when player wins there will be small percentage that goes to the house, technically house can never lose in long term.
this may be one of the reason for them to survive because at least there are surely income in every game,players win house will gain as well.