By having your cows checked for pregnancy, you can make management decisions in the fall before feeding expensive hay through the winter. If a cow is open after bull exposure all summer, she probably isn't one you want to keep in your herd. Not only is she eating the same amount of food as the others, but she likely has a fertility issue that you don't want to support. Cows that are difficult to get pregnant or have trouble maintaining a pregnancy are a problem in your herd. Fertility is a heritable trait, and you want animals that reliably come in pregnant, year after year. By knowing their pregnancy status after several months of bull exposure, you can decide what to do with the cows that are open, or aren't in the calving window you are planning on.
Around here, most cows are bred to calve in the spring. Which means fall is the time for pregnancy checking. Another reason to have your cows go through the chute is the opportunity to vaccinate and deworm. After coming in from being on pasture all summer is a great time to get rid of the intestinal parasites your cows may have picked up. They will maintain their weight more easily and have a better haircoat without worms. Take this opportunity to booster their vaccines as well. By doing this, you are reminding her body of the diseases you previously vaccinated for, and her calf will benefit from this through the colostrum. Always read vaccine labels before vaccinating any cows, but especially pregnant ones.
Knowledge is power, and in this case, money!