The kinds of databases where your business stops working if the database does are OLTP databases (often, databases of transactions in the financial sense), and they aren't hundreds of terabytes or tens of millions of transactions per second. Oracle itself doesn't scale to databases so big or with such high transaction rates that they can't run on one server in 02025. (It does scale to databases so big or with such high transaction rates that Oracle can't run them on one server in 02025, but that's just because Oracle's VAXCluster-optimized design is inefficient on current hardware.)
People run Oracle because it's too late for them to switch.
The kinds of databases where your business stops working if the database does are OLTP databases (often, databases of transactions in the financial sense), and they aren't hundreds of terabytes or tens of millions of transactions per second. Oracle itself doesn't scale to databases so big or with such high transaction rates that they can't run on one server in 02025. (It does scale to databases so big or with such high transaction rates that Oracle can't run them on one server in 02025, but that's just because Oracle's VAXCluster-optimized design is inefficient on current hardware.)
People run Oracle because it's too late for them to switch.