I used to work for a well known Betting Company that had shops around the country as well as on the internet and places at various Horse Racing events.
These machines were simply put in, to the stop people leaving the betting shops.
You have a race, so punter put money on, then once the race has finished it maybe 20 minutes or so before the next one. Nothing to do? Go the pub.
Problem is the said punter might stay in the pub and so the bookies loose out.
These machines make a VAST amount of money for the Betting Companies but like all betting machines, the odds are stacked against you, simple as.
As for thousands of jobs going and closing bookies.....well that I think is open for debate, there maybe a steam line of some of the less profatable ones but that is just buisness.
In this day and age with so much uncertainty and many other things, limiting the amout these machines are allowed just moves the problem elsewhere, people will still bet, still loose money and if not careful end up in not a good place.