The sensible person seeing a car speeding towarsds them on the footpath would think I can do something to help protect me and move out of the path of the car.
In an ideal world we'd all be easily able to recognise and escape all danger that may befall us, but you're assuming that that is something which is always possible to do, in a split second, even for the fit and able bodied.
Personally coming from years of motorsport... people are stupid. Some people will always stand at the end of a long straight because they think they can get a good view - but where does a car go if its driver misses their breaking point (easy error for even the most experienced driver)? Straight on into the crowd. So we don't just let people stand there at the end of a straight and have them run out the way when they see a car coming, it's
already too late by then. Rally organisers can be held fully responsible by the law if they allow someone to be killed or injured this way. Instead, we can easily identify these types of danger areas beforehand (because we know the laws of physics and from previous experience) and they are cordoned off.
Same on public roads. People always do stupid dangerous things, even if it's against their own interests. Always. Or at the very least probably all of us do things some of the time that are not the most optimally safe way of doing things. It's up to the road environment to either prevent people from doing stupid dangerous things, or to prevent serious consequences when things do go wrong.
Only here Britain it's the poor road design that can specifically put you in a position where you must take avoiding action against lorries and dive out of the way at the last second if you want to live, obviously a lot of people are unable to accomplish this perfectly every time. It's danger designed in, and nobody's taking any responsibility for it, which is particularly scandalous given that we know how predictable these accidents are. Telling people that they can just move out of the path of cars and lorries that are closing in on them... I find that repulsive.