Recently Ive noticed that a lot of people I talk to want to buy sound cards because they "care how their audio sounds" or that they "want their music and games to sound the best".
Ive had multiple hearing tests (maybe 5) in the last year which pretty much confirmed I have phenomenal hearing. According to the hearing tests I took I apparently have the best hearing that a human being can possibly have - I heard every single frequency in every test 100% of the time.
That being said: Ive always noticed a difference in car audio going from garbage audio equipment to high end audio equipment. I can notice the difference in quality going from one set of decent Logitech speakers to their highest end speakers. I notice the difference with headphones and earbuds. I think the issue a lot of people dont realize is that their audio equipment sucks and not their sound cards... anyway...
Why do people need sound cards? Why do people think they need sound cards? When I was younger (10-15 years ago) I always bought sound cards because sound cards always seemed to offer a better experience with fancy features you dont need and they potentially gave you higher frame rates in games.
Ive seen multiple computers that friends own (casual gamers, music listeners, etc) in the last few years get their sound cards upgraded with aftermarket ones because they "need better sound quality" and in not one of them have I noticed anything different. Right now my HTPC is using the built in audio and hooked up to home theater equipment and it sounds fantastic.
Just a rant I had after a friend told me he wanted to budget a couple hundred bucks minimum into his gaming PC build for a "bad ass" sound card.
Depends on what you are doing. If you are using digital out then having a sound card is pointless.
If you use the soundcard as a DAC like I do for my two channel audio, then it is incredibly important.
Your audio setup is only as good as the weakest link in the chain. If the weakest link is your soundcard it is important. If you are playing your audio through some $10 PC speakers then it's clear that it is not the weakest link in the chain and it is unimportant until it becomes the weakest link.