Because research once was not as standardized as it is today. Int casters did research and only slowly did the other classes get to do researchy things. There are still a few int caster only things in research, but the vast majority of it is the same for all classes. Just a remnant of a past time... Alchemy, poisoncraft and tinkering also are in the Special category (if you are the right race/class).
Great Answer. Mayhap it is time to split out the skills to their own proper categories. After all, it makes far more sense and would make it easier for Players to find those Achievements.
Why? They are easy enough to find as they are and they are special for those classes who get them. Research never should have been farmed out to other classes. Caster research is still superior and should stay that way. Different archtypes use different boxes to create spells and songs. Augs use the new zone based container. There are 7 base tradeskills + 4 specials (alchemy, poison, research and tinkering). If you split out research you really need to split out the other 3 as well. Having seen how much they messed up with the moving of GMM to another area, I'd prefer them to just leave them be.
The class/race restricted are also under there. Research should probably be tucked with the rest of them, but it also used to be class restricted.
Why "special" kind ? Same as some other tradeskills: buy a stack of high-level components (for research - binding powder with high-trivial) from some greedy bazaar seller (typically under 500pp ea, so it would cost you about 500K) , buy or summon supplimental items and click "combine all" in a lag-free zone. About 1 hr later you'll have the tradeskill at 300 or close. (don't forget to grab the trophy quest with the skill between 50 and 99). And when people buy Ice Encrusted items for 1-2 Krono these days (that's 3-6 mil pp if Krono(s) sold for pp) I wouldn't call 500K too expensive to master a tradeskill . Definitely cheaper than farm those 1000 items.(time=money)