Does Monero intend to develop an i2p market as well? I'm not familiar with the plans. If it intends to solely cater to the TOR-based DNMs, well, ok... TOR is not what it used to be thanks to the NSA, and centralized markets are going to be a dying breed, thanks to exit scams, and the NSA.
Having a fully integrated system is one of the major reasons the shadow project could be so revolutionary, not just in the crypto space. Convenience carries a major value and decreases the barriers to entry=mass market adoption.
It isn't on our project agenda, but you should keep in mind that the nature of Monero is that a lot of projects get done by third parties (this is not just a bold theory but is already reality with projects like xmr.to, moneroaddress.com, monerowallet.com, etc.), so someone else may well do one.