Simple. What effect, no matter how minor, would it have on things? What would he have done after the war? What would he have made of the Nazi regime?
Richthofen showed clear signs of PTSD/burnout - he isolated himself, was depressed and started to take risks that went against his own, very successful, rules (attack surprisingly, no dogfights, keep away from ground fire), which finally got him killed. So a "Richthofen continues fighting until 11/11 1918" TL is unlikely.
But Richthofen could get a lighter wound, be replaced to a non-combat position or simply sent for treatment, and still be "the hero that now fights on but in a different role" - thereby depriving Göring (among others) a lot of glory.
To be frank Germany had a lot of heroes from WW1 1918-1939, but their effect on Germany was fairly small. Richthofen would probably be one of them. Maybe some effect on the air industry (but would a pilot stay in a country without an airforce?) but fairly small butterflies.