It's a voluntary design choice since the beginning of Python to avoid the very common mistake of doing:

    while continue = "yes":

instead of:

    while continue == "yes":

Those mistakes introduce bugs that are hard to spot because they don't cause an immediate error, linters can hardly help with them and even a senior can make them while being tired.

I don't know about linters but GCC warns me about that every time I make that typo. They could just require parenthesis when assignment value is used as boolean.

Probably not, since expressions can already be statements. But that would allow dangerous code like "if a = 3", which I don't think the Python devs would want to allow.