After collapse of Soviet Union some Russians decided to not get Estonian/Latvian/Lithuanian citizenship thus staying alien. Their kids then also become Alien. There are countless of programs to give citizenship and it is very streamlined and costs nearly nothing. Most of those aliens have identity issues and love Russia and Putin, however do not go to live there. Also because of such identity issues they hate Baltics and out of spite do not learn the language thus are unable to attain EU citizenship.

Sad story really, however Estonia has nothing to do with this, Baltics are doing all they can to help them - they just refuse the help.