Yeah I'm in the latter camp where I manually move to money market funds. I don't avoid these platforms because I treat the uninvested cash as a checking account: my bills are paid through this account. I feel better comparing it against a regular checking account that pays zero interest.
To be frank, I do not think it should require people to hold some minimum cash amount. Rather, the brokerage can require that buying securities with this reserve cash should be manual, and not automatic. That still gives savvy investors a way to do it manually.
