Why, to make all that quark chemistry a bit easier?

Because electric charge is quantized, so measuring it in thirds is just dumb.

"I see a clock, but I cannot envision the clockmaker. The human mind is unable to conceive of the four dimensions, so how can it conceive of a God, before whom a thousand years and a thousand dimensions are as one?" -Albert Einstein

It would have revealed a lower layer of higher understanding.

No one has been able to calculate the mass of a quark:

"Nobody has seriously calculated theoretically a quark mass from first principles. So there is no issue of agreement with experiment. They are parameters in experimental fits, but sometimes remarkably consistent across a broad range of experiments-- and the QCD/EW calculations using them as inputs. If someone pretends to know their origin, he/she is bluffing."

But the exercise is extraordinary!