Because the South American qualifying is stupidly long
SA WCQ is only 6 games more (or 4 in one case) than what Euro sides play for Euro Championship qualifying, nevermind adding on the WCQ games.
SA doesn't have qualifying for Copa America, since there are only 10 sides, and these WCQ games are absolutely vital to build team cohesion.
It's a joke that SA is going to split back into groups of 5. It means that in a 4 year span aside from Copa America and World Cup, a SA side can only play a maximum of 8 competitive games.
Whereas a Euro side would be playing 20 or more (then again, you've got alot of shit teams in Europe).
European teams don't start qualifying until next year.
For the reasons above.
If South America didn't start WCQ now and waited until next year all the top European clubs would be throwing their toys out of the pram as usual because nations in South America dare to call up their best players.