The chance of getting rid of the last Ultron body himself wasn't high, nor did Luke have much hope of doing so.
But he didn't even get a share of the experience and credit points at all. How annoying!
However, he wouldn't screw his teammates over just to steal points.
When he had destroyed Ultron's semi-vibranium body earlier, he hadn't been thinking about the contribution rate, but about safety.
After all, only by eliminating Ultron as soon as possible and putting an end to any possibility of a counterattack could they achieve their goal of saving Sokovia's civilians.
Acting too selfishly would instead easily create an opening for the enemy.
Thankfully, he had gained a lot this time.
He had no use for the vibranium for now – it was the key for the tycoon to catch the big fish that was Wakanda.