Logical pathnames work well as long as all your files follow the naming restrictions. Which is not the case for all CL programs and libraries, even less so when you're integrating with other languages and their naming conventions, or (shudder) files that have version numbers in them...
If they work well for you, more power to you. But ASDF cannot possibly depend on them.
Also, logical-pathnames require some magic setup to happen early in the system configuration. Details of such configuration is completely implementation-dependent, and it would be a bootstrapping catch-22 to require casual users to do this configuration before they could use ASDF. More work for less bang. Yet another reason why ASDF does not depend on logical-pathnames, and why I do not recommend that anyone should bother with them for anything remotely "portable". Of course, if you already paid the price, you're free to keep using them and live with their limitations.
—♯ƒ • François-René ÐVB Rideau •Reflection&Cybernethics• http://fare.tunes.org Obama's economic policies will be so remembered that he'll be the president picked for the face on the hundred trillion dollar bill.