i've seen this no NULL's allowed OCD thing being taken to extremes

say you sign up a customer today and promise some service that will be done in the near future but you're not sure of the date. since the column is not null you have to put in a crazy date like 1/1/2049. or if something was done in the past then 1/1/1901

so if a customer calls in a few days the CSR will happily tell them they can expect to see someone come to their site in 2049