I am maxing out my 401k and Roth($30,500) and buying $20k in mega corp stock at a discount each year.
But I only keep an average balance of $1000 in my checking account so I can relate with your friends situation.
I use my Fidelity Amx card for almost all purchases and I never use checks or my debit card.
I don't like a big balance in my main personal checking account.
I can relate. I don't worry too much about how much $$ is in my checking account for purposes other than paying the bills scheduled for that month. At the end of each month, the excess (less $500 or so for "fluff") goes either into a savings account or investments.
All purchases are made with a cc which makes life so much easier.