On Mon, 9 Jul 2018, Hans Åberg wrote:

>
>> On 8 Jul 2018, at 23:00, Otared Kavian <otared@gmail.com> wrote:
>> 
>> The advantage being that if the above formula appears in an environment such as a Theorem (where the text is typeset in italic, or slanted) the text in the above \mbox will be also in italic or slanted.
>
> Math displayed formula text inheriting the style of the text appears in two books from first published in 1966 and 1980 that I checked.
>
> So a math text command should probably support that style.

IIRC, that is also the case for the \text command in amsmath.

Aditya