C-41 is an industrial process, the control plots are very useful for labs trying to make the system really efficient and very consistent over a long period.
As individuals we don't generally do enough volume to keep the developer going for months on end. Just following the replenishing directions will keep us darn close for say two to three weekends then we can toss it and start fresh a month or two later when we get the chance again.
Replenishing takes the guesswork out of the times it's 3:15 and you are done, once you get through it a few times you'll see that it is "as consistent as you are" and then some. I don't remember ever having a developing failure that ruined a negative even when I goofed something up, say doubling or forgetting to replenish between runs.
While we as individuals may get slight variations that a pro-lab wouldn't, we also work differently than a pro-lab, we have different expectations for any given shot than they might for our whole order and its not tough for us to adjust our printing processes.
Replenishing on the bleach, fix, and stabalizer is the perfect choice for everybody because the chems don't go bad by themselves, in fact getting fresh air/oxygen into the bleach is important. These chemicals can be kept replenished indefinitely. The only time I throw these out is when I inadvertently contaminate them.