Not in adulthood. Lactaid is a thriving business, ya know.
So is Beano, but people still get nutrition from legumes. Adults still maintain the ability to metabolize lactose, but at a reduced rate.
From a paper The acceptability of milk and milk products in populations with a high prevalence of lactose intolerance.
A positive standard lactose test is not a reliable predictor of the ability of an individual to consume moderate amounts of milk and milk products without symptoms. In usual situations the quantity of lactose ingested at any one time is much less than in the lactose-tolerance test.