[CWuestefeld]

Entry-level instruments - cheap-ish, poor quality, fine for beginners, basically disposable because they're (ironically) difficult to play and don't sound great.

I suspect this is one of the reasons for the cited 90% quit rate. If it's something you're not sure you'll have an aptitude for or even like, you're probably not going to invest much in your first guitar. But the result of that is an instrument that's far more difficult to get to make nice sounds. AFAIK, guitar is the worst for this - other instruments at the entry level might not have great sound, but aren't going to be downright hard to play.

[vkjv]

This! 1000x this! One of the most frustrating things about learning an instrument is that it initially sounds terrible and you feel like you will never get it. If you have a low quality instrument and are inexperienced, you honestly cannot tell if it is you or the guitar.

This is why I heartily recommend to anyone trying to learn to pick-up a mid-range guitar used. You get much higher quality and the price is usually comparble to a "cheap" beginner one.

[ashark]

I was lucky enough to start on a good guitar, but I later tried a couple ~$100-150 "starter" guitars. If I'd started on those I would have quit. Even knowing how to play (more or less) I couldn't make them sound good, and it took a lot of effort just to keep them from buzzing and such.

[skuzye]

At least for me, it's the number one reason I quit learning the guitar