We did, for a time. But they were worth so much, even then, that few were in circulation. (USD 500/1K/5K/10K/100K)
Since 1969, banks have been ordered to shoot them (the large bills) on sight.
Yes, Obama will be on the $20 bill, and you’ll be able to use them by the barrelful.
My understanding is that those were not general circulation notes, but used exclusively for inter-bank transactions.