If you had a load that was 500 W with a 0.7 PF, you would need a 500 W/cosine(0.7) or ~653 W capable unit to drive it.
Now you see, how it costs more money for a higher power device to drive your load. If the voltage were a constant 120, then guess what parameter goes up? Current, because P=VI. So, the wiring has to be sized for 653 W and not 500 W.
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IF (Big IF) you were a designer of a continuously online UPS, it would be wise to employ power factor correction so that the wall power sees a resistive load, otherwise the power company police will come after you in a commercial environment.
If your UPS auto-switches from line to UPS, you can't design it that way and the user (the 0.7 PF load) as to buy a bigger UPS to run his gizmo. In the first case, he would have to buy a bigger UPS as well, but the "power police" will be happy.
Tis article may be a "little" simpler:
https://www.dteenergy.com/businessCustomers/largeBusinesses/electric/powerFactor.html
A business that uses a lot of standard motors and not VFD's could very easily benefit by installing PF correction at the service entrance. This device switches in capacitors to improve the power factor, Where I used to work, we had 36 heat pumps which translates into at least 72 motors, each messing up the power factor especially if they were all on at once. Thus power factor correction was employed.
Variable Frequency drives would have power factor correction at the front end, nearly eliminating service entrance power factor correction.
The utility has to do some, so it's transmission lines don;t exceed the allowable current. When you look at power generation, neuclear can provide a base power, but it's difficult to turn off. Wind provides power as it sort of feels like it and you can't turn it off easily too because the rotor will spin out of control. Solar using inverter technology can do local power factor correction. e.g. It can do things like output 4000 Amps at zero volts, thus it can correct the power facor. This info basically came from a presentation that I attended and is very brief.
And capacitors can also provide power factor correction. The inverter technology can fine tune the correction.