The meter was standardization much before the velocity of light was precisely determined.

Long back the length a meter was determined and everywhere this standard is already in use like in tailor shop, carpenter shop, school, college, book etc so it is not possible to change the length of a meter.

It has been determined that light travel 299,792,458 meter/second experimentally and theoretically.

Speed of light is supposed to be the most invariant of the physical qualities in the universe.

It does not change other standard like length of a rod or bar will vary depending on temperature

The measurement may depend on geographical location too

so a meter is defined as of distance travelled by light in a sec