It's a fairly modern taboo, historically speaking.

While the unrestricted age of consent is between 16 and 18 in all U.S. states, the laws have widely varied across the country in the past. In 1880, the ages of consent were set at 10 or 12 in most states, with the exception of Delaware where it was 7.[104] The ages of consent were raised across the U.S. during the late 19th century and the early 20th century.[105][106] By 1920, 26 states had an age of consent at 16, 21 states had an age of consent at 18, and one state (Georgia) had an age of consent at 14.[104] Small adjustments to these laws occurred after 1920.

Damn Deleware, 7?!