My guess is they with Radiant Quests they thought they could just scimp on the "actual" quests.
The radiant quests
are "Actual" quests.
The problem, especially with the Companions, was that it locked you
out of the Radiant quests, and kept directing you to the givers of the "main" quests. The guilds could have worked if they'd:
a. Made Radiant quests more readily available, but ultimately as optional as they ended up being.
b. "Hid" the main questline from the players, instead of shoving it down their throats.
c. Acknowledged completion of Radiant Quests, and having a "false" Advancement in the guild that increased payout from Radiant Quests and gave you spiffy titles. You cannot get to "Master" down this path
d. Allowed an ambitious/cunning character to "Fast-track" by
finding the Main Quest, and doing that - And the Main Quest needs a few "Jumping-off" points that allow it to try hiding in the Radiant Quests again. And if you accidentally turn down a "Main Quest", mistaking it for another Radiant Quest, there needs to be a "re-offerable" version of that quest.