The problem of those baltic states is heterogeneity.
Sure on a map they look alike and even their names are too, but they're not.
Really it's pretty funny to see how everything two of them share in common is never shared with the third, and the third is never the same.
See Estonia : the estonians are finnic people and so their language is closely like finnish, unlike the two others who share a baltic language.
See Lithunia : Main religion is Catholicism, the two other got Protestantism
See Latvia : Huge population of Russian ( 25% ) the two other get far less.
Etc
So it's not ASB, but they don't feel like ONE country, no more than Serbian and croatian.