https://patents.google.com/patent/US4448419A
The original design of virtual reels was more about decreasing the jackpot odds, since a high-payout combination was no longer bound to the physical stops on the reels. Machines that offered higher jackpots were more appealing, and also gave birth to things like progressive jackpots and progressive networked games.
It also made IGT (the owner of the patent) a giant in the industry. Many workarounds were tried and typically failed in the lawsuits that followed. The most successful deviation was the "bonus game" where a particular symbol set would trigger a small video game or some other activity that had its own paytable independent of the main slot paytable.
The psychological design of near misses didn't show up until probably a decade afterward, but since '419 is now expired it's become the new secret sauce of slotmakers.