Unless a woman is VERY, VERY committed, they will not pump for exclusive feeding for longer than 6 months. Then women tend to give solids rather than pump because it is simply easier. Pumping is extremely time consuming. Public perceptions of breast feeding have a direct effect upon how long a woman will breast feed. Breast feeding for 2 years is recommended. If I pumped for every public feeding, I would have been pumping for about a decade solid now.
There is another issue that as a man you won't be able to understand. It takes excess milk to feed a baby a bottle. You produce enough milk for each feeding. So in order to have enough milk to skip a feed, you have to have a stockpile of milk large enough. On average a 2 month old baby eats somewhere around 3 oz every 2 hours. If you are out and about for 6 hours you need 9 oz of milk. Mom likely produces that much almost exactly. So she has to pump after every feeding. That 9 oz could take a week to a month to get. Pumping also has a direct effect on infant weight gain. Human milk, like cow milk, has a fatty component as well as a thinner component. You can pump and increase the foremilk which is thin. You can't increase the hindmilk. The hindmilk is what causes a baby to gain weight, as well as feel satisfied after a feeding. Too much foremilk causes colic, poor weight gain and a host of other issues.
Pumping takes a very, very long time. A pump can't get all the milk a baby can. I can feed my baby directly and get more down him in 15 minutes than I could from pumping for a half hour. The hormones that allow letdown are not triggered by pumping. It is depressing, isolating, and frustrating to pump.