Yeah I know, you have a very good point and I've often wondered myself, especially in light of so many "professionals" who tell you to consume protein shakes that contain 50 grams of protein at a wack, some of the recovery drinks that contain at least that much or more.
But remember, of your 175 pounds, how many pounds of that is lean body mass? If your body fat is only 10%, that would be just about right for your consuming 30 grams every 5 meals.
I've heard a lot of guys at the gym tell people arbitrarily to consume 1-1.5 grams per pound of body weight, and it makes me cringe, because for one thing, they know nothing about people's health, and there are many situations in which that amount of protein would be highly contraindicated.
In a normal healthy person, again, to remember is that only your lean body mass can utilize the protein, and if you feed your total body weight versus your lean body mass, you are essentially over-feeding yourself and feeding your fat cells.
I do agree with you that it would seem more likely that every person is different and metabolizes nutrients differently, -- I'm more apt to agree with that than believing in "the number" (of anything) applying to anyone.
It's sort of like counting carb intake and reaching your body's maximum storage. There are guidelines and averages, and they're there to give references. I'd rather under-consume protein by a bit and run a trial for at least 12 weeks before adding more protein. Super high protein intake will not make your muscles grow bigger or faster or stronger.