I found a fare that has no reason or rhyme to it
I want to fly one way SEA YVR
UA's fare is over USD $200.00 plus the tax
If I book it as SEA SFO YVR the fare is USD $52.00 plus the tax
Some people value non-stops.
Some people value their time. (less than an hour vs over 5 hours) But some like their MR -- but they are a minority.
There are different competitive pressures on the various segments.