Why then unite in pools? If the probability of getting a reward in solo-mining is equal to the probability of getting a reward in the pool (in proportion to its Stake in the pool).
For example, 50k blk is a pool. My Stake is 10k blk. The pool will pay me a reward in proportion to my Stake (10 blk). In a pool and in a solo, I get the same reward?
Pool staking only makes sense for those that don't want a Computer/Raspi running 24/7 to stake their coins. But it has two huge drawbacks:
1st you'd need to have to give all your BLK to someone else, which means you have to trust someone 100% that they don't run off with your coins.
2nd you'd harm the network's decentralisation, when the pool would have a significant amount of the network weight.
So, pool staking doesn't make much sense but brings huge risks, especially for your own coins.