Do BitShares Titan transactions qualify as anonymous?
At least no one can see the amount you hold in your account name, even if they know it.
Yes, they are fully anonymous. Only the sender and receiver know the parties involved, everyone else can only see the amounts being sent.
Titan is not "fully anonymous" it is just stealth addresses, which an automated way of not reusing addresses. Every transaction is fully traceable, just like Bitcoin.
Bitshares is supposedly going to add mixing in some manner, but I don't know the details.
Anyway, to answer the original question, the main reason I think is that cryptocurrencies as a whole have not "taken off", and certainly not over the past year or less since the anon coins have been around. Everything that is happening now is still either speculation or early stage startup businesses hoping to make it big in the future. Bitcoin is the oldest, largest and most mature in terms of infrastructure, so naturally it is the largest, but even BTC is tiny by comparison to the fiat economy. Naturally the newer less mature coins are going to be much smaller.
Also the price-per-coin is pretty irrelevant to anything.