When you see bands point mics at the crowd, they are likely for one of two purposes
First, they can be used for performers who wear in-ear monitors, so they can hear crowd response.
The first day Steely Dan performed with In-ears, they thought the crowd hated them cause they didn't hear the response. The next show, their monitor engineer, the late great Roger Nichols, pointed a couple shotguns into the crowd and dialed that up and the problem was solved.
The second reason to point mics at the crowd is to fill in the response on an otherwise dry board mix, typically multitrack.
Myself, I point my on-stage mics at the kick drum, when it's in the middle.