Framework vs blank theme

I was looking at a theme framework called Thematic and it is very complex. I am building WP themes from scratch and they are pretty simple.

What is the advantage of useing Thematic vs starting from a minimal blank theme and adding only what I need?

Thanks

If you only need specific features it would be more effiencent to just add your own actions to your themes functions.php file insteading of wasting your server resources on loading an entire framework that you may only use 2 or 3 functions from.