So far, there have been a number of other coins accepted on markets for varying amounts of time.
LTC,dash(was it?) and others I don't remember, they all faded away because they were never used. ...
Other people have pointed that out before, i.e. that other anon coins have been given a try-out in the DNM's before but they all failed to stick.
The BIG DIFFERENCE this time, I think, is that NOW there is an increasing use of so-called Chain-Analysis ramping up BIG TIME with bitcoin.
Legit sites/services as well as "underground" are vulnerable to this, for even "legal reasons" like KYC/AML and monitoring middle-ground "gray" uses like online gambling. Case in point: many people are of the opinion that gambling online in the USA is illegal for the end-user but that's not precisely true. It's just illegal for banks and other "payment processors" to handle transacting of money into and out of the gambling websites... hence for the most part killing them off entirely *before* bitcoin arrived on the scene.
Therefore, like it or not, "technically legal" or not, IF you have even just innocently *received* a bitcoin that passed thru a gambling website even two or three addresses ago, companies like coinbase and circle and even USA based exchanges like Gemini *CAN* and *WILL* cancel your account and refuse you further services.
The more and more this happens to just simple NORMAL USERS, even squeaky-clean fully compliant users who would never DREAM of going anywhere near the darknet markets, the more a privacy-focused coin like Monero will appeal to *everyone*.
It's coming, IMHO.... it's just simply a matter of time.
One year? Five or ten years, etc...? Hopefully just time enough to stock up enough wealth to retire to a nice private island somewhere