Hell, you know bad things are coming when it is 75F in the morning in December. The last bit of tornado weather telegraphed itself in the morning and didn't touch down until mid afternoon, yet I heard people on motorcycles when the storms hit.
No one is surprised by all the conditions that point toward a tornado. The problem is that in certain areas, the tornado watches are occurring ALL the time and you can't stop every time there is one.
So, yeah, in hindsight everyone saw it coming. But no one thinks THIS time will actually be the time so it does sneak up on people. My father recent went to bed during a tornado warning and one touched down less than a mile away. He got lucky. More reliable indicators of actual tornadoes will be helpful.
And I've been involved in tornadoes on days where there was zero risk of the event. Surprise you're getting a tornado out of a totally random storm that was not predicted.
Tornado alley is where warm air from the gulf collides into cold air coming from the NW. The line where these collide shifts around. Storms can form very unpredictably and rapidly.
On the one hand it's awe inspiring to see a massive thunderhead materialize out of nowhere in just a couple hours. On the other it means what the other commenter is saying is very misleading. Texas, where the other commenter is apparently from, is at the southern end of tornado alley and I believe not quite as dynamic, which may explain their attitude somewhat.