It's a bit complicated. But, generally, speaking it's because the Baltic states and Finnland were more organized and enjoyed a huge military support of Western powers, both Germany and Entente (though, there were some peculiarities in this regard as well). Also, they got a lot of publicity, simply because they were in Europe and Lenin openly promised them independence. So, in this regard it was important for the Bolshevik regime to prove to the world that they are "authentic." By contrast, Central Asia was a very remote place, there literally were no foreigners there except very few. The resistance there was very disorganized and poorly armed. It didn't have a chance against the very well organized and well armed Red Army. Frunze who commanded the Reds there was also considered one of the most talented Bolshevik generals.