Yup my dad had a nasty accident in 2004 and the impact almost severed the lower part of his leg. His biking boots saved the lag from severing. However, the impact still turned his lower leg to pate (was a combined 100mph impact), and his ankle bone has not regenerated and is so weak he still has to walk with a crutch. That is 8 years later.
I used to work in a factory and I was once told by the safety man that in a side impact the toe cap acts like a sharp vice and can amputate toes. He could have just been scare mongering though!
He said that because they are only really designed for things falling on top of them, side crushes are their weak point (anyone in the know care to clarify?).
Also work boots probably wont offer any protection from your ankle/foot being over extended/rotated either.
I'm a big advocate of wearing full biking gear, but it does not have to cost the earth, but quality gear does help if you can afford it. My mate dropped his GS on the autobahn and went skidding down the road (was wet and a lorry driver cut him up) and his gear saved his skin that day.
I cringe when I see people riding in track suits or jeans or shorts/t-shirts and after seeing a few in physio rehab where my dad used to go it is scary how much damage a road can do to your body if you are not protected, even at 30mph.
Buff