For those reasons: * Physics stopped CPUs from advancing any further. * When CPUs used to advance they almost cost the same, that's why once they reached a ne

For those reasons: * Physics stopped CPUs from advancing any further. * When CPUs used to advance they almost cost the same, that's why once they reached a new milestone they never looked back to produce slower CPUs. * Adding a number next to "i" will make costumers pay more for pretty much the same CPU. * There's only major CPUs manufactures and all CPUs they make are sold anyway so they start by mass production from day one.