Why would I want to disable my observatory?

As far as I can tell, all of the effects are positive. Why is there an option for turning the observatories off?

Observatory (1)
---------------
Increases the chance of the astronomical events by 0.5%, +25% to the science
output, +1K to the max science. Turning off observatories will only disable
event bonus.

scaffold 0.06 / 55.00
slab 38.50
iron 825.00
science 1100

Effects:
--------
Science bonus (%): 0.25
starEventChance: 20
starAutoSuccessChance: 1
Max Science: 1000

Yearning to one day catch the red light fairy