The OP is right. There are not so many sites or projects involving bitcoin. I am not telling its not there. Its there.But not that much. The only reason behind this is bitcoin is not that popular. Nowadays its getting more popular because of its price and more people started using bitcoins. And because of that in near future, we can expect more projects or sites based on bitcoin.
That's right. The projects which involve bitcoin mostly come from the crypto world and it's the kinda normal thing that bitcoin is involved but if you're looking for many projects which are outside this crypto world you'll rarely find some that are involving bitcoin or at least use bitcoin as crowdfunding payment method or any kind of these.
Unfortunately, people still prefer to use Paypal or credit card to invest onto many projects nowaday.