Interpretation is such a huge part of football rules. You can have all the instant replays in the world, and it will rarely lead to happy, congruent fans and pundits. (Source: The Next Web, Technology in Football? Don't Overstate It's Impact)
Introducing instant replays to soccer isn't about making "happy, congruent fans and pundits".
It's about being 100% accurate that the ball crossed / didn't cross the line.