Because when i heal and save my rein, nano a genji and bionade the enemy team so he can shred them with his ult i feel so passive and disconnected despite setting up a big play.
When i play ashe, flank the enemy, twoshot the zen, dynamite the 76 and Ana, send in a bob and boop away the rein so that 3 more people die i get a dopamin rush and feel amazing. So even if there are matches in which i do not perform i prefere to click heads over healing the people who do so. Might also be the mentality of people in real life