I don't know about the need for a "tower", but the Falcon 9 launch sequence includes firing up all the engines and making sure they're running fine. Same too f

I don't know about the need for a "tower", but the Falcon 9 launch sequence includes firing up all the engines and making sure they're running fine. Same too for the SSMEs as I recall. That's one of the great advantages of liquid fuel rockets, you can turn them off. Ditto the mighty Saturn V, they started "8.9 seconds" before launch, 300 milliseconds apart. So you need some serious hardware to hold it down till release, and to deal with all that exhaust.