Horse racing seems less dangerous based on those criteria. The other risky forms of gambling tend to also be electronic - things like online poker, which is more prone to addiction than playing poker in person. Brain scans of gambling addicts show the release of neurochemical rewards actually occurs a moment before the actual pull - what's known as an anticipatory reward. Slots has real immediacy to the addictive response, because the games go so fast.This puts people into a cognitive flow state, where they are detached from reality.
There is a continuity to the gambling - you can immediately start the next pull of the slots.
The other factors that have been argued are: The over-stimulation from the lights and sounds are part of it.
