Matched transistors question

[johns at oei.com]

     Got a techie question...
     
     I have been following all the VCF/VCO control talk lately and once in 
     a while somebody mentions using matched transistors.  I always thought 
     that transistors found in transistor array ICs were closely matched by 
     default (as well as thermally matched).  Is this really true?   If it 
     is true, why would anybody go to the trouble of trying to match 
     transistors then?
     
     Better yet, when I review the popular ladder filter scematics, I 
     always see that the last rung of the transistor "ladder" always uses a 
     transistor IC pair whereas the other transistors are always discrete.  
     Wouldn't it be easier just to use a single transistor array IC 
     instead?
     
     John Speth - johns at oei.com