After doing some research I believe this is less to do with interest only being in Yoko Kanno's works and more the general publishing around anime music. For the most part full band scores tend to be for general compilations with fairly few exceptions (which tend to be theme song collections), with most anime music scores dealing with piano which makes sense for various reasons, but also the same amount of it not making sense (time and effort in arranging it). The compilations that do exist are more or less identical, almost every book has the same 30-50% of it's contents consisting of the same songs.
Piano arrangements are more varied and can exist for seemingly minor shows, something that also happens with commercial music score printing in Japan - a comparatively minor artist can easily get piano arrangements but not a straight replication of the actual material.
As far as the original Macross goes, Ai wo omoimasen ka is frequently found in compilations, but isn't close to the most suitable choice to arrange in a band score (the other songs are much more band orientated). I can only put it down to a combination of the age of the material and the lack of commercial music on the soundtrack.
I can understand that this stuff typically has a low level of interest anyway (newer stuff is easier to market), but sometimes the stuff missing seems a lot more marketable than the stuff that is actually printed.
Although thanks to this I've discovered a proper band score exists for Lupin, and not just the first Jazz album, the trouble is finding a copy for sale. Never mind, it's a tribute album score