The government of Belarus has announced that it will not permit more than two foreign military bases on its territory. There are now two Russian military bases in Belarus, and it is unlikely that any other country has suggested placing bases there. It is therefore reasonable to assume that the Russians have asked Belarus for additional facilities and that the Belarusians have turned them down.
Belarus has seen in Crimea 2014 what Russia can do if they have a base inside your country to stage an invasion from. Belarus is much bigger than Crimea so they may figure that just two Russian bases isn't enough to stage a complete takeover rapidly.
I am fine with the status quo for Belarus that prevents Russia from fully using Belarus as a staging area to attack west or south. Belarus is a friendly buffer for Russia but not a corridor for Russia to invade NATO or Ukraine.
As I've noted, Belarus may be the most important territory in Europe today.
