Casting a pointer does not produce an lvalue. Why?

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An even better example, unary + yields an rvalue, as does x+0.

The underlying reason is that all these things, including your cast, create a new value. Casting a value to the type it already is, likewise creates a new value, never mind whether pointers to different types have the same representation or not. In some cases, the new value happens to be equal to the old value, but in principle it’s a new value, it’s not intended to be used as a reference to the old object, and that’s why it’s an rvalue.

For these to be lvalues, the standard would have to add some special cases that certain operations when used on an lvalue result in a reference to the old object, instead of a new value. AFAIK there’s no great demand for those special cases.

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