...but discrete soundcards, especially external ones, are still alive and well if you record. The noise floor of internal sound cards hasn't gotten that much better (a PC is very noisy RF environment), and if you need mic preamps, quarter inch jacks, optical in, etc, they generally don't fit on a PCI card or laptop.
But for general gaming or home theater use? Nope. Send the audio out over the HDMI out, or SPDIF for DVI/VGA rigs, and let the amp sort it out.