[55555]

There are major federal government websites that have office hours. The EIN application website only works between 9am and 5pm. I like to imagine that it's this way because there's no webapp, there's just a team of people who get all the HTTP requests and manually respond to them. This would also explain its speed.

[KMag]

If they're only paying support staff 9 to 5, it might make sense to shut it down outside of supported hours, even if it would probably still work, especially if they're not positive that it won't do something odd like start issuing duplicates if the back-end DB is down.