Maintainability - points to Future that is if Code is needed to be changed for some improvement etc which may or may not come through and even if it come in how many cases (% wise may 20 %, may 40 %)

while

Functioning points to present where system has to work in present to be fruit full to developer , user , company to get back investment made in terms of money , time & resources. So it has to approach towards 100 %.

If code work then effort can be made afterwards to be maintainable for future.
But if code is not working first priority will be to make it work or worry for future maintainabilty.
More over most embedded system project are of custom design nature where continuity / repeatition of same design / methedology is less likey
Opposed to this is pure comm software project OS , Database , appl software where there is continuous improvement in software is needed and most components are reusable hence maintainabilty is of greater importance there