Mainly because on a daily basis, restaurants and eateries typically make from three to five times the amount of coffee that homes make and aside from the brands (which vary) the eateries have basically succeeded in the trial and error process so that by now (in relation to how long they've been in business and the coffee brands they buy) they know what their customers want in taste, plus most coffee is now pre measured so all you have to do to get a good cup of coffee is to experiment with the amount of water you use.