Why does C++11 developers prefer space before colon in range-based for loops?

In most of the C++11 codes, I see:

for (auto i : list) { // a space before colon
    ...
}

However, usually C++ developers do not prefer:

for (int i = 0 ; i < list.size() ; ++i) { // spaces before semi-colons
    ...
}

but

for (int i = 0; i < list.size(); ++i) { // no spaces before semi-colon
    ...
}

.

If you are one of them, why do you NOT prefer:

for (auto i: list) { // no space before colon
    ...
}

?