If you made $5.97 an hour and got a 10% raise you'd be up to 6.57.
Do it again, 7.22.
Then 7.95, 8.74, and 9.61.
Finally 10.57 after 6 years. The compounding helps. Instead of being 20% more after two years it's 21%, because it builds on the initial 10%.
There was a crummy dept store (Ames) that offered 70% off all fine jewelry, plus another 20% off, and finally another 10%. They expected that gambit would attract a clientele that sucked at math.
Similarly a BOGO sale that gets you the 2nd item at half off only possibly gives you at most 25% off, and less if there's a price discrepancy between items, as the cheaper one is discounted.