Cash management accounts are better for large balances than FDIC accounts at banks for the most part. Since the brokerage abstracts where the balances are actually stored they split your large balances over a number of FDIC accounts and you get up to $1.5M in FDIC cover at some places instead of $250K. If you’re thinking of Robinhood they just did a bad job of execution, and shockingly thought SIPC alone would do, and that’s what angered the SIPC head.