“Time on Machine” (TOD) is the #1 metric concerned by casinos and machine-slot manufacturers.
Casinos and gambling machine manufacturers have found out the average amount of time a gambler spends on the system is the #1 indicator of a game’s profitability. The slot machine manufacturers (IGT, Bally, WMS, and others) are focussing on features that will raise this amount when developing new games.
One way to look at a game that has a high “time on-screen” is how well a gambler gets hooked into “the zone.” It is a state of mind where only the gambler and the machine are in. This form of thinking, according to some anecdotal reports, is taking the place of worries about winning big.
Slot machines are the only opaque odds-on casino game.
Most casino games use a card deck or a pair of dice or something similar to produce their random outcomes. There are game examples where you know the probability of winning a bet.
There are 52 cards in a box, after all, so the chances of having one card are 51 to 1. You will measure all of the other odds if you know the deck’s composition.
For a craps game, there are only 6 sides to a die, so there’s a finite number of combinations. It is fairly easy math to calculate the probability of any given outcome.
But on a slot machine, when you have certain combinations of those symbols on the screen at the same time in a line, you have symbols that pay off at a certain rate. Yet there’s no way you can assess the chances of having a similar symbol on any particular spin.
Slot machines currently account for 85 percent of the total casino income.
By the mid-1980s the casino industry changed drastically. Dice machines were viewed as a diversion for women at the time. The true gamblers were the boyfriends and husbands who stuck with games such as blackjack who craps.
In those days the slots had not even stools in front of them. They were put in the hall or near to the elevator— the intention was to avoid taking up space on the floor of the game. We were in areas where people had passed from point A to point B.
It only took the slot machines a decade to begin producing twice as much revenue per year as all table games put together. In 2003, gambling machines generated 85 percent of the revenues of the casinos.
By the way, you can also see 65 percent or 70 percent quoted on various websites. My best guess is that at one time this number was valid but the Web is like a giant chamber of echoes. If someone has written a page to quote a statistic elsewhere, other webmasters will write similar pages to paraphrase those earlier pages. Few online writers spend a lot of time doing real, genuine work in print media.