A printer media profile controls other things like ink limiting, gray balance, linearity of colour and more:
Because the profile was specifically produced for the exact printer/ink/media combination you have loaded, it will use the precise amount required to produce colour (saving on ink consumption) but can also eliminate bleeding, cockling, pooling, and flooding.
It also knows how to lay down the exact CMY mix to produce a neutral gray without the use of any black ink at all if you choose. Many people have experienced printed gray results that have a coloured cast throughout. Some printer manufacturers add additional light black or gray inks to their printers to overcome this, although this is completely unnecessary in a calibrated and profile state and often adds to the running costs of the printer.
Another thing that is improved by using the correct profile is better linearity, or colour distribution. When using generic profiles, people often see “Posterisation“. This is a visible line that appears between graduations of colour.