Most families that hunt for meat, including mine, are not wealthy. We are not talking about sport hunters, we are talking about subsistence hunting. It's still very common in large swathes of America. Just looking around for the lowest prices possible, the cost of steel shot is more than double the cost of lead shot for #3 shells (commonly used for waterfowl). For #00 shells (used for deer and medium game) it's more than three times as expensive. Ammo costs add up quick, as you need to practice with the same shells you hunt with.

Working in tech, I can afford to buy higher quality and more expensive things, and the ammunition I use is no exception. But for many people it's not really within their budget. Lead is cheap, it's one of the main reason its used to make projectiles in the first place.