Depends on how many total people are in the lobbies.
For example in League Play there are around a total of 800 players across the world at any given time. That makes 8 seperate maps lists for each "map collection" that players have . So right there that cuts it down to about 100 people who have the maps that you have.
So across the world you have 100 players to choose from where 80 percent of those are already in a round. Leaving around 20 people to join up with.
Try using the avoid button. It may help.
if you mean you lobby hopped and ended back in the same lobby it will happen when not alot are playing that list.
If you mean after each match it does that because it is meant to do so.
if you mean you started playing after a not playing and ended up in a lobby of same players from earlier date refer to sentence one for answer.
it is a bug. not really.
Is it a problem. not really.
Will it be fixed or does it need to be fixed. probably not.