There are many different specialities out there in programming. Most of the time it is relatively easy to substitute one for the other. However occasionally there is a line which is not trivial to cross. If you have no idea where they are, it is easier to just accept fragmentation of specialties.

I mean, how many PHBs are really equipped to understand why it is more appropriate to hire a good Java or C++ programmer for a Perl programming position than a sysadmin who did a bunch of Perl scripting? After a couple bad experiences, and knowing that you lack the expertise to make a good decision, wouldn't you feel the temptation to make the safe one?

Cheers,
Ben