Let's say I give you a 90 day warning of a 200bps rise. You price that into your economic activity, you decrease your forward investment and deleverage, this causes a recession (as expected). 89 days later the economy is looking much slower than it was when I made the announcement and inflation is dropping. What do I do now? I told you I was going to raise rates, but conditions clearly now make that the wrong thing to do. But if I don't do it then the next time I guide you about future rates you're going to ignore me.