If you change your filters under "is reachable" to "all" you will see all other servers... my guess is those are server that you cannot join like on other side of world (high ping) and some outdated servers on older version of game.
Yep, basically what crazy junkman Wolfgang said. "Dead" servers in the list are expected and can be caused by many different things:
bad firewall/router settings on the server (client can't retrieve details in that case) mismatching game version they crashed / have been shut down but the list entry has not been removed properly (those will be auto removed after a few minutes but until then they will appear as dead servers)
The "reachable/same version" filter is enabled by default to hide these servers.
If you disable it you will see all servers red servers with name / details have the wrong game version red servers with just the IP and no details are unreachable