Why do most rifle bullets have a pointed nose, but most pistol bullets have a round nose?

Update: I recently discovered that there’s a niche for rifle rounds that are subsonic (for use with suppressors) but combine good penetration with maximum stopping power. These specialty rounds feature heavy blunt nosed bullets. Two examples are the .458 SOCOM and the .50 Beowulf.

Neither one of those are even close to subsonic.

You’re right about the .50 Beowulf. The .458 SOCOM does support a subsonic variant though. And in any case, the bullets in question are intended to be as heavy as possible within the cartridge length limitation, hence the blunt nose.