It doesn't slow down my computer.
Yes it does. You're just not sensitive to speed differences. I have zero tolerance for un necessary latency and find it intolerable to run. It's the primary reason why I run SLC HDDs in RAID0 and use 192GB of system memory with 64GB of it dedicated to caching disk i/o. I record music and the latency is simply UN-acceptable even on the fastest hardware available.
If you're simply surfing, playing games even on a "modern" computer you probably won't know.
Some people settle for MP3, some have to have FLAC...