And work well FC does too!
Strangely enough the big HBA players, like Qlogic, Emulex and the like are promoting both topologies without pressuring the channel towards FCoE. To be honest, FC is still their primary revenue stream and they are not going to do anything to quell that business flow at all.
Another issue is the [current] cost of 10GB and Converged switching equipment, it's still not "that cheap", whereas the cost of a capable 8 port enabled/16 port ready, 4GB/s FC switch is under the £2.5K mark with SFPs and cables.
The emerging technologies of Virtualised IO, like those very clever Xsigo directors is another factor that may be keeping the industry away from FCoE. Just connect your current FC Switch and iSCSI arrays to the Xsigo box, drag and drop the LUNs to the relevant [Virtual] Servers and ta-da!
The industry has been banging on about FCoE for some time now, I only ever see it being implemented in a green [new] installations, however those who have a reasonable sized investment in 4/8G FC will stick with what they have and/or perhaps look at the Virtual IO opposed to the fuss of mixed storage connectivity within their DC