I've only made a limited study in economics, so I'm a little confused here.  I'm hoping someone with a better understanding can clear this up for me.

Until recently, like many here apparently do, I assumed that as more businesses started offering goods and services in exchange for bitcoin the value would rise.  After all, the value in any currency is in what you can buy with it, and therefore increasing the size of the economy should increase the value of the currency.

Recently, though, it occurred to me that you can already buy pretty much anything with bitcoin.  How?  By exchanging it for fiat.

After all, isn't this what many companies will do anyway?  They may accept bitcoin as a payment option, but some time after you give it to them, they'll exchange it.

So, are bitcoin businesses really that important to giving value to bitcoin?  If not, then what does give it value?  Like I said, I hope someone can clear this up for me.  Thanks.