Why operator= returns reference not const reference

Question

The original question is related to overloading operator= and I like to share my findings as it was nontrivial for me to find them. I cannot imagine reasonable example to us

Answer 1

Why should it be const? If you're assigning to it, obviously it's modifiable. That would be artifically limiting.

As for use cases, why not:

T &local = t1 = t2 = t3;

In this example, local isn't const.