Sunblock is not exactly what you think it is...

“spf 75…ugh, anything over 30 is basically useless.”

I believe that quote, taken from something I heard being said on the TV, is double meaning code. "Getting sun" is metaphor for being looked at/watched (the light from other people's eyes). Sunblock is attempting to STOP the sun from looking at you/shining on you/burning you. So, I believe that spf numbers actually represent years that are added to your face to make you appear older.

Imagine if putting sun block on created the illusion, to an audience watching you, that you were many years older than you actually are? You wouldn't notice this overlay of age, but THEY would.

So if you were 25 years old and put on spf 30 sunblock, you'd actually appear 55 years old...and therefore you wouldn’t get that much sunburn because viewers, who care about looks most, wouldn’t be staring at you/watching you as much.

Saying spf 75 isn’t any better than 30, is simply saying 30 years older seems to be enough added years to get people to look at you less.