The Social Security file-and-suspend strategy has been used primarily for couples to coordinate the delay of individual retirement benefits (earning delayed retirement credits) while making a spouse eligible to begin his/her spousal benefits. It can also be used as a partial form of "undo" for a retiree who started benefits early, and later wishes to suspend them (at full retirement age) to earn delayed retirement credits (a benefits increase that can partially or fully offset the decrease triggered by electing benefits early in the first place).
However, the strategy to file and suspend can also be used as a proactive planning strategy for individuals, because it creates an opportunity for the retiree to subsequently "undo" the decision to delay and "retroactively" claim benefits back to the date they chose to file and suspend (e.g., full retirement age). Thus, for someone who is approaching age 66 and isn't certain about whether it's a good idea to delay or not, choosing to file and suspend allows them to wait until age 70 to make the final decision, enjoying the benefits of the delay if it still makes sense to do so, but having the opportunity to go back and claim benefits at 66 if there's a change in health or circumstances.
The key distinction is that while the standard Social Security rules only allow an individual to file for up to 6 months' worth of retroactive benefits, the file-and-suspend rules allow for a "reinstatement of voluntarily suspended benefits" that can undo the suspension going back anytime during the suspension period. Thus, choosing to file and suspend can effectively replace the normal 6-month retroactive benefits rules with a more favorable set of reinstatement rules, that at worst will simply leave the individual delaying until age 70 as was planned in the first place, but with the flexibility to change their mind for a few years along the way!