It depends on the value of the vehicle, the use case, the cost of the PPF job and your own personal values.
Personally, I'm not neurotic enough about the look of my car to pay the cost for PPF. If it gets bad enough, I will have the paint repaired. If I invest the $5000 cost of PPF at just 6% (stock market has averaged 10% for the last 30 years) I would have over $9,000 in 10 years to put to a new car or new paint job.
A car is meant to be driven.
BMW claims to be the ultimate driving machine, not the ultimate stand around looking at it machine. I actually watched a video on YouTube of a guy with a special frozen grey M3 that would not drive the car because he couldn't match the paint if it got a rock chip.
My brother in-law has 2 identical Shelby GT-500s with about 2,000 miles combined on them!!!!
I use my stuff, I don't abuse my stuff. Which means if it is 10 years old with 120,000 miles on it is not going to look new. That's ok to me. But it also isn't going to look ragged out and busted. I am not a guy that is going to wash my car every 20 minutes. I don't generally do "appearance" mods. If it doesn't make my car go faster, turn better, stop quicker or in some way enhance the driving experience, I don't care.