Timewalking and the Mage Tower are time-limited, which is exactly why they get missed. Event dungeon runs, the Timewalking rewards worth having and a Mage Tower completion are booked here for the week the event is actually live.
The Infinite Timereaver — the rarest Timewalking drop — is farmed as its own service, because getting it by luck takes years.
Why book these during the event week?
Timewalking rotates in and out, and the Mage Tower is only up on certain weeks. Ordering while the event is live is the only way to get the rewards this cycle rather than waiting for the rotation to come back around.