Isn't it bad for ecosystem? Why do miners stay in 2 big pools and give them more than %50 power? Even if they don't use it for evil.
It theoretically poses some risk, but practically it does not. These pools are profit oriented and with their individual hashrates they have a guaranteed chance of getting one of four blocks confirmed, that's a chance to hit a reward every ~40 minutes.
Even if hypothetically both miners could merge to attack the network, there is no guarantee that they will be successful, their chain will likely be abandoned by all nodes and they will have miners pull out en masse from their pool into other ones.
It seems safer to take a guaranteed profit every 40 than gamble with no long term possibility.
Wouldn't it be better if total of the biggest pools are less than %50? Would you prefer 4 pools for %50 rather than 2 pools for %50?
Miners are profit oriented too. They stand a higher chance of making a profit if they associate with the top pools as long as they meet the specification to join.
I will rather 4 or 8 pools for 50%, but it's not a real bother.